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UNMOUNTABLE_BOOT_VOLUME (0x000000ED) Blue Screen Error: Causes and Troubleshooting Guide

Quick Answer The UNMOUNTABLE_BOOT_VOLUME error, identified by Windows stop code 0x000000ED, is a Blue Screen of Death (BSOD) error that occurs when Windows c...

Bison Technical Team Enterprise IT specialists

Updated 09 Nov 2026 16 min read 0 total views

Structured technical guidanceSafety notes included where requiredSources listed below

Quick Answer

The UNMOUNTABLE_BOOT_VOLUME error, identified by Windows stop code 0x000000ED, is a Blue Screen of Death (BSOD) error that occurs when Windows cannot mount or access the volume containing its operating system during startup.

The boot volume is the disk partition from which Windows loads its operating system files. If Windows cannot access this volume because of file system corruption, storage problems or other boot-related issues, the startup process may fail and display the UNMOUNTABLE_BOOT_VOLUME stop error.

Common reasons include:

Corruption in the NTFS file system or boot volume metadata.
Bad sectors or physical problems with an HDD or SSD.
Unexpected shutdowns or power interruptions.
Damaged boot records or startup-related information.
Loose or faulty storage connections.
Storage controller or firmware-related problems.

Start troubleshooting by checking whether the storage drive is detected correctly, then use Windows Recovery Environment (WinRE) and Startup Repair. If the drive is healthy but file system corruption is suspected, CHKDSK may help repair the volume.

Important: If the drive is making unusual noises, repeatedly disconnecting, or showing signs of physical failure, prioritize data recovery before running intensive disk repair operations.

What Is the UNMOUNTABLE_BOOT_VOLUME Error?

UNMOUNTABLE_BOOT_VOLUME is a Windows stop error that indicates that the operating system's input/output subsystem attempted to mount the boot volume but could not complete the operation.

Windows needs access to the boot volume to load essential operating system files, drivers and other components required during startup. If the volume cannot be mounted, Windows cannot continue the normal boot process and may stop with a blue screen.

Microsoft identifies this error as Bug Check 0x000000ED. The second bug check parameter contains a file system status code that can provide additional information about why the volume failed to mount.

The error may occur on computers using traditional hard disk drives (HDDs) or solid-state drives (SSDs). It does not automatically mean that the storage device has physically failed.

UNMOUNTABLE_BOOT_VOLUME Error Identification

Property	Details
Error name	UNMOUNTABLE_BOOT_VOLUME
Stop code	0x000000ED
Error category	Windows Blue Screen of Death (BSOD)
Related component	Boot storage volume and file system
Common file system	NTFS
Possible storage devices	HDD, SATA SSD, NVMe SSD
Typical symptom	Windows cannot complete startup

Common Symptoms of UNMOUNTABLE_BOOT_VOLUME

When this error occurs, the computer may exhibit one or more of the following symptoms:

A blue screen appears with the stop code UNMOUNTABLE_BOOT_VOLUME.
The computer restarts automatically after displaying the error.
Windows repeatedly fails to start and enters Automatic Repair.
The system becomes stuck in a startup repair or recovery loop.
Windows fails to load beyond the manufacturer logo or Windows loading screen.
The computer displays the same stop error after every restart.
The storage drive may occasionally disappear from BIOS or UEFI firmware settings if a hardware or connection problem exists.

The exact symptoms depend on the underlying problem. A corrupted file system may prevent Windows from mounting the partition even when the physical drive is still functional.

Common Causes of the 0x000000ED Error

1. File System Corruption

Damage to the file system is one of the documented reasons for the UNMOUNTABLE_BOOT_VOLUME error. Windows may fail to mount the boot partition when important NTFS metadata or file system structures become corrupted.

This can happen following unexpected shutdowns, interrupted disk operations, storage errors or other events that affect the integrity of the volume.

2. Hard Drive or SSD Problems

A failing storage device may prevent Windows from reading the information required to mount the boot volume.

Possible hardware-related problems include:

Bad sectors on a hard disk.
Uncorrectable read errors.
Failing SSD memory or controller components.
Intermittent storage device detection.
Storage device communication failures.

If the drive has physical problems, software-based repairs may not resolve the issue. Repeated repair attempts can also complicate data recovery.

3. Unexpected Shutdown or Power Interruption

Sudden power loss, forced shutdowns or system crashes during disk write operations can leave file system information in an inconsistent state.

If Windows cannot properly interpret or recover the affected file system structures during the next startup, it may fail to mount the boot volume.

4. Damaged Boot Information

Windows uses boot-related structures and configuration information to locate and load the operating system.

Damage to relevant boot records, boot sectors or configuration information can contribute to startup failures. However, boot configuration problems and file system mounting failures are not identical issues and should be diagnosed separately.

5. Faulty Storage Connections

A loose SATA cable, damaged connector, unstable power connection or faulty motherboard storage port can interrupt communication with an HDD or SSD.

For computers using external or removable boot storage, an interrupted connection may also prevent Windows from accessing the required volume.

6. Storage Controller or Firmware Problems

Problems involving storage controller hardware, firmware or drivers can affect communication between Windows and the storage device.

Changes to BIOS or UEFI storage settings, including SATA operating modes, may also affect the ability to access an existing Windows installation.

Do not randomly change AHCI, RAID or other storage controller settings. An incorrect change can create additional boot problems.

How to Fix UNMOUNTABLE_BOOT_VOLUME (0x000000ED)

Follow the troubleshooting methods below in order. Start with non-destructive checks and proceed to more advanced repair methods only when necessary.

Before You Start: Protect Important Data

Before attempting disk repairs, consider whether important files are stored on the affected computer.

If the drive is making clicking, grinding or other unusual noises, stop repeated startup attempts.
If the drive intermittently disappears from BIOS or UEFI, investigate the hardware before running repair commands.
If the data is important and there is evidence of physical drive failure, consider professional data recovery or creating a suitable disk image before attempting repairs.
Keep the BitLocker recovery key available if the Windows installation is encrypted.

Some recovery operations modify file system information. Data protection should take priority over making the computer boot again.

Method 1: Restart the Computer and Check Storage Connections

Start with basic hardware checks. An intermittent storage connection or temporary hardware communication problem can prevent Windows from accessing the boot volume.

Turn off the computer completely.
Disconnect the power supply. For a laptop, follow the manufacturer's instructions for safely disconnecting power.
If you are comfortable working with computer hardware, inspect the SATA data and power connections for an HDD or SATA SSD.
Check whether the drive and its connectors are properly seated.
For an NVMe SSD, check that the module is properly installed if you have the required hardware experience.
Reconnect the power supply and start the computer.

Note: Do not open a laptop or desktop that is under warranty if doing so could affect its warranty coverage. If you are unfamiliar with internal hardware, ask a qualified technician to inspect the connections.

Method 2: Check Whether the Storage Drive Is Detected in BIOS or UEFI

BIOS or UEFI firmware initializes the computer's hardware before Windows starts. Checking whether the storage device is detected can help identify a possible hardware or connection problem.

Turn on the computer.
Press the manufacturer's BIOS or UEFI setup key during startup. Common keys include F2, Delete, F10 or Esc, depending on the manufacturer.
Open the storage, system information or device information section.
Check whether the HDD or SSD containing Windows is listed.
Verify that the expected boot device is available in the boot configuration.

Interpret the results:

Drive detected: The firmware can identify the storage device, but this does not guarantee that its file system or data is healthy. Continue with Windows recovery diagnostics.
Drive not detected: Investigate the storage connection, device, controller or motherboard before attempting Windows software repairs.
Drive detected intermittently: This may indicate a hardware, connection or firmware problem that requires further investigation.

Do not reset BIOS settings or change storage controller modes without first recording the existing configuration and understanding the consequences.

Method 3: Run Windows Startup Repair

Startup Repair is a built-in Windows Recovery Environment tool that can diagnose and repair certain problems preventing Windows from starting.

It may help when startup-related files, boot configuration information or other supported startup components are damaged.

How to Access Windows Recovery Environment

If Windows automatically displays Automatic Repair after repeated startup failures, select Advanced options.

If the recovery environment does not appear, you can access it using Windows installation media:

On another working computer, create Windows installation media using Microsoft's official installation media instructions.
Connect the bootable USB drive to the affected computer.
Start the computer and select the USB device from the boot menu.
When the Windows Setup screen appears, select your language and keyboard preferences.
Click Next.
Select Repair your computer, not Install Windows.
Open Troubleshoot and then Advanced options.

Run Startup Repair

Open Troubleshoot.
Select Advanced options.
Choose Startup Repair.
Select the Windows installation if prompted.
Provide the BitLocker recovery key if required.
Allow Windows to diagnose and attempt repairs.
Restart the computer and check whether Windows starts normally.

Startup Repair cannot resolve every storage or file system problem. If it reports that it could not repair the computer, proceed to the next diagnostic method.

Method 4: Run CHKDSK to Check and Repair the Boot Volume

CHKDSK (Check Disk) is a Windows command-line utility used to examine file system structures and identify certain disk errors.

Microsoft specifically identifies running CHKDSK with the /r parameter from Windows Recovery Environment as a possible troubleshooting step for the UNMOUNTABLE_BOOT_VOLUME error.

Important precautions:

CHKDSK with repair options modifies the file system.
The /r option performs a more extensive examination and attempts to recover readable information from affected sectors.
It can take considerable time, particularly on large or problematic HDDs.
If physical drive failure is suspected and the data is important, prioritize data recovery rather than running CHKDSK repeatedly.

Step 1: Open Command Prompt in Windows Recovery Environment

Boot into Windows Recovery Environment using the procedure described earlier.
Select Troubleshoot.
Open Advanced options.
Select Command Prompt.

Step 2: Identify the Correct Windows Drive Letter

The Windows partition may not use the same drive letter in the recovery environment as it does during normal Windows operation. For example, the installed Windows partition may appear as D: or E: instead of C:.

To identify the correct partition, enter:

diskpart
list volume
exit

Examine the listed volumes and identify the partition that contains the Windows installation. Drive size, volume labels and file system information may help.

You can verify a possible Windows partition by running:

dir D:\Windows

Replace D: with the appropriate drive letter. If the Windows directory is not found, check another likely volume.

Do not assume that the Windows installation is always on drive C: when working in WinRE.

Step 3: Run the CHKDSK Command

Once the correct Windows partition has been identified, run:

chkdsk D: /r

Replace D: with the actual drive letter of the Windows partition.

The command performs the following operations:

Examines the file system for errors.
Attempts to repair logical file system problems.
Checks for bad sectors.
Attempts to recover readable information from affected sectors.

Allow the process to finish without interrupting it unless there is a compelling safety reason to stop the operation.

Understanding CHKDSK Parameters

Parameter	Purpose
`/f`	Fixes file system errors found on the volume.
`/r`	Locates bad sectors and attempts to recover readable information. It also includes the functionality of `/f`.
`/x`	Forces the volume to dismount first when necessary and includes the functionality of `/f`.
`/v`	Displays additional information about files as the check progresses, where applicable.

After CHKDSK completes, review its output for reported file system errors, bad sectors and repair results.

Restart the computer and check whether the Windows startup problem has been resolved.

Method 5: Repair Boot Records Using Bootrec

If the storage drive is accessible but startup-related boot records are damaged, the Windows Recovery Environment provides the bootrec utility for certain boot repair operations.

Microsoft lists boot record repair as a possible troubleshooting approach for this stop error. However, boot record repairs are not a universal solution for every UNMOUNTABLE_BOOT_VOLUME problem.

Use this method only after identifying a relevant boot configuration or boot record problem.

Step 1: Open Command Prompt

Start Windows Recovery Environment and navigate to:

Troubleshoot > Advanced options > Command Prompt

Step 2: Run the Appropriate Boot Repair Command

To write a compatible master boot record to the system disk, use:

bootrec /fixmbr

To attempt to write a new boot sector, use:

bootrec /fixboot

Important: These commands address specific boot code problems. They do not repair damaged NTFS file system metadata or physically failing storage devices. In particular, /fixmbr does not repair a damaged partition table.

Modern UEFI/GPT installations use an EFI System Partition and a different boot architecture from traditional BIOS/MBR systems. Do not apply legacy MBR repair procedures indiscriminately to UEFI installations.

If the computer uses UEFI, investigate the EFI boot configuration and follow the appropriate Microsoft recovery documentation for that installation.

Method 6: Use System Restore

If the error started after a software installation, driver change or system configuration modification, System Restore may help return Windows system files and settings to an earlier working state.

This option is useful only when a suitable restore point is available.

Boot into Windows Recovery Environment.
Select Troubleshoot.
Open Advanced options.
Select System Restore.
Choose the Windows installation if prompted.
Select an appropriate restore point created before the problem started.
Review the changes and follow the instructions to complete the restoration.
Restart the computer and check the result.

System Restore primarily rolls back system files, registry settings and installed programs. It is not a substitute for backing up personal data and should not be treated as a repair for physical storage failure.

Method 7: Check the Storage Device Health

If the previous methods do not resolve the error, investigate the physical condition of the storage device.

Possible diagnostic approaches include:

Using the storage manufacturer's official diagnostic utility.
Checking available SMART (Self-Monitoring, Analysis and Reporting Technology) information.
Running the computer manufacturer's hardware diagnostics.
Inspecting storage cables and motherboard connections.
Testing the drive using a suitable diagnostic environment.

SMART information can help identify certain developing storage problems, but a healthy-looking SMART report does not guarantee that a drive is free from failure.

If the storage device cannot be detected reliably, reports critical hardware errors or fails manufacturer diagnostics, consider replacing it after protecting or recovering important data.

Additional Troubleshooting Considerations

Check for Recent Hardware Changes

If the error appeared after installing a new storage device, replacing a motherboard, changing a storage controller or modifying BIOS settings, investigate those changes.

Check whether the storage device is connected to the expected controller and whether the previous storage configuration has been preserved.

Check for Recent Software or Driver Changes

Storage drivers and low-level system components can influence communication between Windows and the storage device.

If the problem began immediately after a driver update or system change, consider using an available restore point or the appropriate recovery options to reverse the change.

Do not install random third-party storage drivers or modify offline system driver configurations without identifying the actual problem.

Check the Windows Recovery Logs

When Startup Repair fails, its diagnostic log may provide additional information about the detected startup problem.

The common log location is:

%windir%\System32\LogFiles\Srt\SrtTrail.txt

When working from Windows Recovery Environment, the Windows installation may use a different drive letter. Locate the actual Windows partition before attempting to access the log.

The log may contain information about startup components that could not be repaired. However, not every UNMOUNTABLE_BOOT_VOLUME error will have a useful Startup Repair log entry.

Difference Between UNMOUNTABLE_BOOT_VOLUME and INACCESSIBLE_BOOT_DEVICE

Both errors are related to Windows boot storage, but they represent different bug checks.

Feature	UNMOUNTABLE_BOOT_VOLUME	INACCESSIBLE_BOOT_DEVICE
Stop code	`0x000000ED`	`0x0000007B`
Meaning	Windows cannot mount the boot volume.	Windows cannot access the boot device during startup.
Common investigation areas	File system integrity, boot volume readability and storage health.	Storage drivers, controller configuration, boot device accessibility and hardware.
Possible troubleshooting	Startup Repair, CHKDSK and storage diagnostics.	Storage driver investigation, controller configuration checks and boot device diagnostics.

Although the errors have overlapping troubleshooting areas, their causes and appropriate repair procedures should not be assumed to be identical.

When Should You Replace the Hard Drive or SSD?

Replacing the storage device should be considered when diagnostics indicate a physical problem rather than simply assuming that every boot volume error requires a new drive.

Consider professional inspection or replacement when:

The storage device is not detected consistently in BIOS or UEFI.
The drive produces unusual mechanical noises.
Manufacturer diagnostics report a hardware failure.
The drive has recurring uncorrectable read errors.
The computer repeatedly experiences storage-related failures even after appropriate file system repairs.
The drive becomes inaccessible or disconnects unexpectedly.

If the drive contains important files, consider professional data recovery before replacing or attempting additional repairs. Installing a new drive does not recover data from the old one.

How to Prevent UNMOUNTABLE_BOOT_VOLUME Errors

Although not every storage failure can be prevented, the following practices can reduce the likelihood of file system corruption and help protect important information.

Use reliable power: Use a suitable UPS for desktop computers and business systems where power interruptions are common.
Shut down Windows properly: Avoid unnecessary forced shutdowns and power interruptions during disk operations.
Monitor storage health: Use suitable diagnostic tools to identify potential storage problems.
Maintain regular backups: Keep important files backed up to a separate storage device or reliable backup service.
Use compatible drivers: Obtain storage controller and chipset drivers from the computer or component manufacturer.
Maintain firmware: Apply appropriate storage and motherboard firmware updates after checking compatibility and manufacturer instructions.
Check hardware connections: Ensure that internal storage connections are properly secured.
Investigate recurring errors: Do not repeatedly ignore disk-related warnings or unexplained startup failures.

Frequently Asked Questions

1. What does UNMOUNTABLE_BOOT_VOLUME 0x000000ED mean?

It means Windows attempted to mount the boot volume during startup but could not complete the operation. Possible reasons include file system corruption, storage device problems or boot-related failures.

2. Is UNMOUNTABLE_BOOT_VOLUME caused by a faulty hard drive?

Not necessarily. A faulty HDD or SSD can cause this error, but file system corruption, storage connection problems and other boot-related issues can also prevent Windows from mounting the boot volume.

3. Can CHKDSK fix the 0x000000ED error?

CHKDSK may resolve the problem if file system corruption or certain disk errors are responsible. Microsoft specifically identifies chkdsk /r as a possible recovery step. However, CHKDSK cannot repair a physically failing storage device.

4. Can I fix UNMOUNTABLE_BOOT_VOLUME without reinstalling Windows?

Yes, in many cases. Startup Repair, file system repair, appropriate boot record repairs and System Restore may resolve the problem without reinstalling Windows. The appropriate method depends on the underlying cause.

5. Will repairing UNMOUNTABLE_BOOT_VOLUME delete my personal files?

Some recovery procedures are designed to preserve personal files, but no repair operation should be considered completely risk-free. CHKDSK may modify file system structures, while resetting or reinstalling Windows can affect installed applications and personal data. Back up or recover important files before performing potentially disruptive operations.

6. Why does my computer repeatedly restart after showing this error?

Windows may automatically restart after a stop error. If the underlying boot volume problem remains unresolved, the same failure can occur during every subsequent startup, resulting in a restart loop.

7. Can an SSD cause the UNMOUNTABLE_BOOT_VOLUME error?

Yes. Both HDDs and SSDs can experience file system corruption, controller problems, connection failures and physical hardware faults that prevent Windows from mounting the boot volume.

8. What should I do if BIOS does not detect my SSD or HDD?

Check the storage connections, power supply, storage controller and motherboard compatibility. If the device remains undetected, have it inspected by a qualified technician. Windows software repair commands cannot repair a storage device that the system firmware cannot detect.

9. Is UNMOUNTABLE_BOOT_VOLUME the same as INACCESSIBLE_BOOT_DEVICE?

No. UNMOUNTABLE_BOOT_VOLUME uses stop code 0x000000ED, whereas INACCESSIBLE_BOOT_DEVICE uses 0x0000007B. Both involve boot storage accessibility, but they represent different Windows bug checks.

Key Takeaways

The UNMOUNTABLE_BOOT_VOLUME (0x000000ED) error indicates that Windows cannot mount the volume required to start the operating system. It can result from file system corruption, storage hardware problems, boot-related damage or connection issues.

The most appropriate troubleshooting approach is to identify whether the problem is related to the storage hardware, file system or boot configuration before attempting repairs.

Start with storage detection and connection checks, use Windows Recovery Environment and Startup Repair where appropriate, and consider CHKDSK when file system corruption is suspected. Use boot record repair methods only when the relevant boot components are identified as the problem.

Above all, protect important data before performing disk repair operations, particularly when the storage device shows signs of physical failure.

Official References

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