Remote Desktop (mstsc.exe) problems usually come from one of three root causes: the mstsc.exe binary is missing, its supporting DLLs (mstscax.dll) are missing / unregistered, or the language resource (.MUI) file for your system language is missing. Below is a complete, practical guide with every safe method I’d try — from quick checks to final, guaranteed fixes — plus the working final solution that restored Remote Desktop for you.

Quick summary of approaches (choose by urgency)

1. Quick check & run — look for mstsc.exe in System32 / SysWOW64.

2. SFC / DISM — try automated system repairs.

3. Copy from WinSxS — extract the legit copies stored in Windows’ component store.

4. Restore .MUI — ensure the language resource (e.g. en-US\mstsc.exe.mui) exists.

5. Register DLL & fix App Path — register mstscax.dll, add App Path registry key.

6. Copy from another PC (same Windows build) — safe fallback.

7. Repair install (in-place upgrade) — guaranteed Microsoft-supported fix.

8. Third-party remote tools — temporary alternatives if you need access immediately.

1) Diagnose first — what to run now (Admin PowerShell / CMD)

Run these and copy their outputs if you need help:

• Search for binary copies (PowerShell Admin):

Get-ChildItem -Path C:\ -Filter mstsc.exe -Recurse -ErrorAction SilentlyContinue | Select-Object FullName
Get-ChildItem -Path C:\Windows\WinSxS -Filter mstsc.exe.mui -Recurse -ErrorAction SilentlyContinue | Select-Object FullName

• Simple existence checks:

Test-Path "C:\Windows\System32\mstsc.exe"
Test-Path "C:\Windows\System32\en-US\mstsc.exe.mui"
where mstsc

• SFC / DISM quick health:

sfc /scannow
DISM /Online /Cleanup-Image /RestoreHealth

2) Fast fixes (try these in order)

A — Copy mstsc.exe from SysWOW64 → System32 (if present)

Sometimes 64-bit path is missing but 32-bit exists:

Copy-Item "C:\Windows\SysWOW64\mstsc.exe" "C:\Windows\System32\mstsc.exe" -Force

Run PowerShell as Administrator.

B — Run SFC then DISM

If files are corrupt or missing, these repair from the component store:

DISM /Online /Cleanup-Image /RestoreHealth
sfc /scannow

C — Re-register Remote Desktop ActiveX control

If mstscax.dll exists but isn’t registered:

cd /d C:\Windows\System32
regsvr32 mstscax.dll

cd /d C:\Windows\SysWOW64
regsvr32 mstscax.dll

D — Create App Path so Windows finds mstsc reliably

New-Item -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\mstsc.exe" -Force | Out-Null
Set-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\mstsc.exe" -Name "(default)" -Value "C:\Windows\System32\mstsc.exe"
Set-ItemProperty -Path "HKLM:\SOFTWARE\Microsoft\Windows\CurrentVersion\App Paths\mstsc.exe" -Name "Path" -Value "C:\Windows\System32"

3) If mstsc.exe exists but shows:

“The system cannot find the file specified. C:\Windows\System32<LANG_NAME>\mstsc.exe.MUI”
That means the .MUI file for your system language (for example en-US) is missing. Windows expects it at C:\Windows\System32\<LANG>\mstsc.exe.mui.

Safe ways to restore the .MUI

A — Extract from WinSxS (best quick local source)

Windows stores component copies in C:\Windows\WinSxS. Use PowerShell (Admin) to locate & copy the correct .MUI:

# Example for en-US / amd64 & wow64
$source64 = Get-ChildItem -Path "C:\Windows\WinSxS" -Filter "mstsc.exe.mui" -Recurse -ErrorAction SilentlyContinue |
    Where-Object { $_.FullName -match "amd64" -and $_.FullName -match "en-US" } | Select-Object -First 1

$source32 = Get-ChildItem -Path "C:\Windows\WinSxS" -Filter "mstsc.exe.mui" -Recurse -ErrorAction SilentlyContinue |
    Where-Object { $_.FullName -match "wow64" -and $_.FullName -match "en-US" } | Select-Object -First 1

# Create language folders & copy
New-Item -Path "C:\Windows\System32\en-US" -ItemType Directory -Force | Out-Null
Copy-Item $source64.FullName "C:\Windows\System32\en-US\mstsc.exe.mui" -Force

New-Item -Path "C:\Windows\SysWOW64\en-US" -ItemType Directory -Force | Out-Null
Copy-Item $source32.FullName "C:\Windows\SysWOW64\en-US\mstsc.exe.mui" -Force

B — If WinSxS lacks the English MUI — copy from another PC

Get C:\Windows\System32\en-US\mstsc.exe.mui from another Windows 11 Pro 22H2 machine with the same build (or same 22H2 family — builds close to 22621 usually work). Copy to your C:\Windows\System32\en-US\ (requires admin).

Do NOT download random mstsc.exe.mui files from the internet.

C — Fix file permissions to allow copy (TrustedInstaller-owner)

Protected folders belong to TrustedInstaller. Safe method to copy and restore ownership:

# Run as Admin; adjust $source to your .mui location (e.g., C:\a\mstsc.exe.mui)
$source = "C:\a\mstsc.exe.mui"
$targetDir = "C:\Windows\System32\en-US"
New-Item -Path $targetDir -ItemType Directory -Force | Out-Null

# Take ownership & grant Admins temporarily
takeown /F $targetDir /A /R
icacls $targetDir /grant Administrators:F /T

# Copy
Copy-Item $source (Join-Path $targetDir "mstsc.exe.mui") -Force

# Restore owner
icacls $targetDir /setowner "NT SERVICE\TrustedInstaller" /T

4) Automated script (the final working solution we used)

This is the full block that you can run as Administrator if you already have mstsc.exe.mui accessible locally (for example at C:\a\mstsc.exe.mui). It:

• Ensures folders exist,

• Takes ownership temporarily,

• Copies to both System32 and SysWOW64 en-US folders,

• Restores TrustedInstaller ownership,

• Launches mstsc.exe if successful.

# === Restore mstsc.exe.mui from C:\a\mstsc.exe.mui ===
$source = "C:\a\mstsc.exe.mui"
$target64dir = "C:\Windows\System32\en-US"
$target32dir = "C:\Windows\SysWOW64\en-US"
$target64 = Join-Path $target64dir "mstsc.exe.mui"
$target32 = Join-Path $target32dir "mstsc.exe.mui"

if (-not (Test-Path $source)) { Write-Host "ERROR: Source not found: $source"; exit 1 }

foreach ($d in @($target64dir, $target32dir)) {
    New-Item -Path $d -ItemType Directory -Force | Out-Null
    takeown /F $d /A /R | Out-Null
    icacls $d /grant Administrators:F /T | Out-Null
}

Copy-Item -Path $source -Destination $target64 -Force -ErrorAction Stop
Write-Host "Copied to $target64"
if (Test-Path "C:\Windows\SysWOW64") {
    Try { Copy-Item -Path $source -Destination $target32 -Force; Write-Host "Copied to $target32" } Catch {}
}

# Restore owner
icacls $target64dir /setowner "NT SERVICE\TrustedInstaller" /T | Out-Null
if (Test-Path $target32dir) { icacls $target32dir /setowner "NT SERVICE\TrustedInstaller" /T | Out-Null }

if (Test-Path $target64) { Start-Process "C:\Windows\System32\mstsc.exe"; Write-Host "Done." } else { Write-Host "MUI not copied." }

This is the final solution that worked: placing a valid mstsc.exe.mui (English US) into C:\Windows\System32\en-US, restoring ownership, then launching mstsc.exe.

5) If you can’t get the MUI file (no other PC available)

Do an in-place Repair Install (Windows setup) — it will rebuild WinSxS and restore all official language resources without deleting apps or files:

1. Download Windows 11 ISO from Microsoft (official): https://www.microsoft.com/software-download/windows11

2. Mount the ISO, run setup.exe

3. Choose Keep personal files and apps and proceed.

4. When finished, mstsc will be restored.

This is the most reliable Microsoft-supported repair.

6) Temporary alternatives to get remote access now

While you fix mstsc, use:

• Chrome Remote Desktop

• AnyDesk

• RustDesk
  These are safe third-party remote-access tools that do not require mstsc.exe.

7) Safety & cautions

• Never download mstsc.exe, mstscax.dll or .mui files from untrusted websites. Those can be malware.

• Only copy files from a trusted machine (same Windows edition/build) or extract from your own C:\Windows\WinSxS.

• Take ownership temporarily only when necessary and restore TrustedInstaller owner afterwards (commands above handle that).

8) Troubleshooting checklist (if still failing)

• Confirm C:\Windows\System32\en-US\mstsc.exe.mui exists (Test-Path).

• Confirm mstsc.exe exists in C:\Windows\System32.

• Try regsvr32 mstscax.dll in System32 and SysWOW64.

• Re-run sfc /scannow after copying MUI.

• Reboot after ownership/permission changes.

• If errors remain, gather logs:

  • findstr /c:"[SR]" %windir%\logs\cbs\cbs.log > "%userprofile%\Desktop\sfclogs.txt"

  • Get-Content "C:\Windows\Logs\DISM\dism.log" -Tail 80

Final recommendation (what worked for you)

1. You verified mstsc.exe came back but failed due to missing mstsc.exe.mui.

2. The working fix was to obtain a valid mstsc.exe.mui for en-US (either from WinSxS or another same-build PC) and copy it to C:\Windows\System32\en-US\mstsc.exe.mui.

3. Use the PowerShell script above (or the single-block script I gave earlier) to safely take ownership, copy the file, restore TrustedInstaller, and launch mstsc.exe.

4. If you cannot obtain the MUI, perform a Microsoft in-place repair install — that will fix everything.

==================================

I created the PowerShell script and packaged it into a ZIP you can download and run.

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Restore-Mstsc-MUI.ps1

----------------------------

# Restore-Mstsc-MUI.ps1

# Safe, ready-to-run PowerShell script to copy mstsc.exe.mui into System32\en-US and SysWOW64\en-US

# Source file path is set to C:\a\mstsc.exe.mui - change $source if your file is elsewhere.

# Run this script AS AN ADMIN (right-click PowerShell -> Run as Administrator) or it will exit.

# --- Elevation check ---

$principal = New-Object Security.Principal.WindowsPrincipal([Security.Principal.WindowsIdentity]::GetCurrent())

if (-not $principal.IsInRole([Security.Principal.WindowsBuiltInRole]::Administrator)) {

    Write-Host "ERROR: This script must be run as Administrator. Right-click PowerShell and choose 'Run as administrator'." -ForegroundColor Red

    exit 1

}

# --- Paths (edit $source if your .mui is in another location) ---

$source = "C:\a\mstsc.exe.mui"

$target64dir = "C:\Windows\System32\en-US"

$target32dir = "C:\Windows\SysWOW64\en-US"

$target64 = Join-Path $target64dir "mstsc.exe.mui"

$target32 = Join-Path $target32dir "mstsc.exe.mui"

Write-Host "Source file: $source"

if (-not (Test-Path $source)) {

    Write-Host "ERROR: Source file not found. Place mstsc.exe.mui at $source or edit this script to point to the correct path." -ForegroundColor Red

    exit 1

}

# --- Create target folders if missing ---

foreach ($d in @($target64dir, $target32dir)) {

    try {

        New-Item -Path $d -ItemType Directory -Force | Out-Null

        Write-Host "Ensured folder exists: $d"

    } catch {

        Write-Host "Warning: Could not ensure folder $d : $($_.Exception.Message)" -ForegroundColor Yellow

    }

}

# --- Take ownership & grant Administrators full control for the duration of the copy ---

foreach ($d in @($target64dir, $target32dir)) {

    try {

        Write-Host "Taking ownership (temporary) of $d ..." -ForegroundColor Cyan

        & takeown /F $d /A /R | Out-Null

        & icacls $d /grant Administrators:F /T | Out-Null

    } catch {

        Write-Host "Warning: Could not change permissions on $d : $($_.Exception.Message)" -ForegroundColor Yellow

    }

}

# --- Copy the MUI to System32 (64-bit) ---

try {

    Copy-Item -Path $source -Destination $target64 -Force -ErrorAction Stop

    Write-Host "Copied to $target64" -ForegroundColor Green

} catch {

    Write-Host "Failed to copy to $target64 : $($_.Exception.Message)" -ForegroundColor Red

}

# --- Copy to SysWOW64 (32-bit) if present ---

if (Test-Path "C:\Windows\SysWOW64") {

    try {

        Copy-Item -Path $source -Destination $target32 -Force -ErrorAction Stop

        Write-Host "Copied to $target32" -ForegroundColor Green

    } catch {

        Write-Host "Failed to copy to $target32 : $($_.Exception.Message)" -ForegroundColor Yellow

    }

} else {

    Write-Host "SysWOW64 not present on this system; skipping 32-bit copy." -ForegroundColor Cyan

}

# --- Verification ---

$ok64 = Test-Path $target64

$ok32 = Test-Path $target32

Write-Host "`nVerification results:"

Write-Host "System32\en-US\mstsc.exe.mui : $ok64"

Write-Host "SysWOW64\en-US\mstsc.exe.mui  : $ok32"

# --- Restore ownership to TrustedInstaller (best-effort) ---

try {

    Write-Host "Restoring owner to TrustedInstaller for target folders (best-effort)..." -ForegroundColor Cyan

    icacls $target64dir /setowner "NT SERVICE\TrustedInstaller" /T | Out-Null

    if (Test-Path "C:\Windows\SysWOW64") {

        icacls $target32dir /setowner "NT SERVICE\TrustedInstaller" /T | Out-Null

    }

    Write-Host "Ownership restored (best-effort)." -ForegroundColor Green

} catch {

    Write-Host "Warning: could not restore ownership automatically: $($_.Exception.Message)" -ForegroundColor Yellow

}

# --- Launch mstsc if copy succeeded ---

if ($ok64) {

    Write-Host "`nLaunching Remote Desktop..." -ForegroundColor Green

    Start-Process "C:\Windows\System32\mstsc.exe"

    exit 0

} elseif ($ok32) {

    Write-Host "`nLaunching 32-bit Remote Desktop (SysWOW64)..." -ForegroundColor Green

    Start-Process "C:\Windows\SysWOW64\mstsc.exe"

    exit 0

} else {

    Write-Host "`nERROR: MUI not copied to expected locations. Consider using another PC with the same Windows build or perform an in-place repair install." -ForegroundColor Red

    exit 1

}

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How to use it: