STATUS_MUI_FILE_NOT_FOUND (0XC00B0001): Missing MUI File Fix

You'll see error STATUS_MUI_FILE_NOT_FOUND (0XC00B0001) when launching an app — often a Microsoft tool like PowerShell ISE, Notepad, or a third-party program. The app fails silently or shows a dialog saying the resource loader couldn't find a matching MUI file. Happens most after a Windows feature update (e.g., 22H2 to 23H2) or after manually removing a language pack to free disk space. Some users hit it after a failed cumulative update that left the MUI directory in a half-baked state.

What's actually happening here

Windows uses .mui files (Multilingual User Interface) to load localized strings — button labels, menus, error messages — for each language you have installed. When an app starts, the resource loader looks for a file like C:\Windows\System32\en-US\appname.exe.mui. If that file doesn't exist, or the parent language folder is missing entirely, you get error code 0XC00B0001.

The root cause is almost always a corrupted or incomplete language pack. Windows updates sometimes overwrite or delete MUI files during the install, and the cleanup logic doesn't always re-download them. Another common scenario: you uninstalled a language pack via Settings → Time & Language, but some stub folders remain with nothing inside.

Fix it — three approaches, try in order

1. Run SFC and DISM

This rebuilds the system file store, including MUI files from the Windows component store. It's the first thing to try and fixes about 60% of cases.

1. Open Command Prompt as Administrator (Win+X, then A).
2. Run sfc /scannow and wait for it to complete. It'll scan all protected system files and replace corrupted ones.
3. Then run DISM /Online /Cleanup-Image /RestoreHealth. This pulls fresh copies from Windows Update if your local store is damaged.
4. Reboot and test the failing app.

Why this works: SFC checks the file hash of each .mui against a catalog, and DISM can replace missing ones from the component store. If the app still fails, the problem is likely a missing language folder that SFC won't recreate.

2. Re-add and remove your language pack

This forces Windows to rebuild the MUI files for the current display language. It's the real fix for most cases where SFC and DISM didn't help.

1. Go to Settings → Time & Language → Language & region.
2. Under Preferred languages, note the language you're using (likely English (United States) or similar).
3. Click Add a language, pick a totally different language (e.g., German, French), install it. This downloads a full MUI pack.
4. Set that new language as the Windows display language (it'll ask you to sign out — do it).
5. Sign back in, then go back and remove the new language you just added.
6. Now set your original language back as display language, sign out, sign in again.

What this does: By switching to another language, Windows regenerates all MUI files for that temporary language. When you switch back, it regenerates again for your original language — including any files that were missing. I've seen this fix the error on Windows 10 22H2 and Windows 11 23H2 after a botched update.

3. Manually restore the missing MUI file

Only do this if you know exactly which MUI file is missing — check the event log first.

1. Open Event Viewer (eventvwr.msc) and look under Windows Logs → Application for an error with event ID 1000 or 1001 that mentions 0xC00B0001. The event details often list the missing file path.
2. Suppose it says C:\Windows\System32\en-US\powershell_ise.exe.mui is missing.
3. Grab the same MUI file from a working Windows machine (same version and build) or extract it from an ISO of the same Windows version. Copy it to the target folder.
4. Run icacls "C:\Windows\System32\en-US\powershell_ise.exe.mui" /grant "NT AUTHORITY\SYSTEM:(F)" to set proper permissions — otherwise Windows might ignore it.
5. Test the app.

This is a last resort because finding the exact file and build match can be tedious. Use it only if steps 1 and 2 fail and you're comfortable digging through event logs.

If it still fails

Check a few things:

• Third-party antivirus — some aggressive AVs quarantine .mui files as false positives. Check quarantine logs in Defender or your AV of choice.
• Corrupt user profile — create a new local user account and see if the app runs there. If it does, the MUI error was profile-specific (uncommon but possible).
• Windows build mismatch — you might have a leftover MUI file from a different build (e.g., 22H2 file on a 23H2 system). Run winver and compare the build number. If mismatched, delete the entire language folder (e.g., en-US) and run DISM /Online /Cleanup-Image /RestoreHealth to let it rebuild from scratch.

I've never seen this error require a full Windows reinstall. The language pack switching trick in step 2 has saved me three times now — it's the most reliable fix that doesn't involve hunting down individual files.