Fix NS_E_WMP_UI_NOTATHEMEFILE (0XC00D0FE0) in WMP

Quick answer

Delete the contents of %LOCALAPPDATA%\Microsoft\Media Player and restart Windows Media Player — that clears the corrupt theme cache that triggers this error.

Why this happens

Windows Media Player (WMP) uses XML-based theme files to define its layout. When you switch skins or the player tries to load a saved layout, it reads a file from the local cache. If that file gets truncated, corrupted, or points to a missing resource, you get error 0XC00D0FE0. The layout manager correctly parses the XML but fails the theme validation — it's not a valid theme file.

This usually shows up after a Windows update, a manual skin swap that went sideways, or when you've copied a theme file from another machine. I've also seen it after third-party WMP plugins overwrite the default theme. The culprit is almost always the cached theme store, not the actual theme file you're trying to use.

Fix it in 5 steps

Close Windows Media Player completely. Check the system tray — it likes to sit there pretending it's closed.
Open File Explorer and paste this into the address bar:
```
%LOCALAPPDATA%\Microsoft\Media Player
```
Select everything inside that folder. Don't delete the folder itself, just its contents. You'll see files like CurrentDatabase_372.wmdb and a few folders. Nuke them all.

Press Win + R, type regedit, and navigate to:

HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Player

Delete the Player key entirely. Windows will recreate it with defaults on the next launch. Note: This resets your playlists and last position — but you'll be back online in less than a minute.

Now restart WMP. It'll act like a fresh install, rebuild the theme cache, and that error should be gone.

If that doesn't cut it

Sometimes the cache rebuild isn't enough. The issue might be in the actual theme file you're trying to load. Here's what to check next:

Try the default theme — Right-click in WMP, go to View > Skin Chooser, and pick Windows Media Player 10 or whatever came with your OS. If the default works, your custom skin is the problem.
Reinstall the skin — Delete the skin file (usually a .wmz file) from C:\Program Files\Windows Media Player\Skins and download a fresh copy. Don't trust a skin that's older than your Windows version.
Run System File Checker — Open Command Prompt as admin and run sfc /scannow. If a system component related to WMP got flagged, this fixes it. It takes a few minutes, so grab a coffee.

I've seen cases where the error only appears when launching WMP from a shortcut with a specific switch (like wmplayer.exe /prefetch:1). Remove the shortcut and create a new one. That's rare, but it happens.

Prevention tip

Don't manually copy theme files into the WMP directories. Use the built-in import option (File > Open or drag-and-drop onto the player). And if you're messing with skins, do it one at a time. I've watched junior admins spend an hour on this because they installed a pack of 20 themes and one of them was corrupt. The layout manager doesn't tell you which one — it just gives you that generic error.

Also, if you're on Windows 11, WMP is essentially legacy. Consider using the Media Player app from the Store instead. It's not as feature-rich, but it doesn't have this theme baggage.