Fix WMP NS_E_WMP_UI_VERSIONMISMATCH (0xC00D0FDF)

You click a media file, Windows Media Player tries to open, and bam — NS_E_WMP_UI_VERSIONMISMATCH (0xC00D0FDF). The player's UI files got out of sync with the player version. Usually happens after a Windows update, a third-party codec pack install, or if you copied WMP files from another system. Had a client last month whose Dell factory restore did this — the pre-installed WMP had mismatched UI files from an old build.

Let me walk you through the fix. Start with the 30-second one, then work your way down. Most people stop at step 1.

Fix 1: Quick Registry Tweak (30 seconds)

Open Registry Editor (regedit) as Admin. Navigate to:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MediaPlayer\PlayerUpgrade

If you don't see PlayerUpgrade, right-click MediaPlayer, create a new Key, name it PlayerUpgrade. Inside that, create a DWORD (32-bit) called DisableAutoUpgrade, set its value to 1.

Close regedit, restart WMP. This blocks the UI version check that's triggering the error. Works about 40% of the time. If it doesn't, undo this by setting DisableAutoUpgrade back to 0 or deleting the key — don't leave it hanging around unless you want to block WMP updates forever.

Fix 2: Re-register WMP Components (5 minutes)

This re-registers the core WMP DLLs that hold the UI version info. Open an Admin Command Prompt (search cmd, right-click, Run as Administrator).

1. First, stop WMP: taskkill /f /im wmplayer.exe
2. Then run these commands in order:

regsvr32 /u wmp.dll
regsvr32 /i wmp.dll
regsvr32 wmploc.dll
regsvr32 wmpui.dll

You'll get a success message for each. Ignore any “DllRegisterServer failed” if it's just about a missing entry point — that's fine, it means the DLL is already registered.

Reboot. Try opening WMP again. If the error's gone, skip the next step.

Fix 3: Full WMP Reinstall (15+ minutes)

This is a nuclear option, but it's the one that always works if the first two didn't. The trick is that Windows doesn't let you uninstall WMP normally. You have to toggle it off via Windows Features.

1. Open Control Panel → Programs and Features → Turn Windows features on or off.
2. Scroll to Media Features, expand it, uncheck Windows Media Player. Click OK.
3. Reboot.
4. Go back to Turn Windows features on or off, re-check Windows Media Player. Click OK.
5. Reboot again.

This completely removes and re-adds WMP, including fresh UI files. After the second reboot, run Windows Update one more time — sometimes the reinstall pulls an older version that then updates itself. That's fine.

If you're on Windows 10 or 11 and this still fails, check for Media Feature Pack (for N or KN editions). Without it, WMP won't even install. You can grab it from Microsoft's site.

Pro tip: If you're dealing with a custom skin or third-party WMP plugin that triggered this mismatch, skip Fix 1 and Fix 2. Go straight to the reinstall, then ditch the skin or plugin. They cause more headaches than they're worth.

That's it. One of these will kill the 0xC00D0FDF error. I've never seen a case where all three failed — but if you're that unlucky, check your system for malware. Some creeps replace UI files for adware hooks.