Fix NS_E_WMP_GOFULLSCREEN_FAILED (0XC00D11BF) in Windows Media Player

Simple Fix (30 Seconds): Tweak the Full Screen Registry Key

I know seeing that error pop up when you're trying to watch a video in peace is infuriating. Most people run into this after a Windows update or a codec pack installation that messes with WMP's full screen flag. The quickest fix is a registry change—don't worry, it's safe if you follow this exactly.

1. Press Windows + R, type regedit, and hit Enter. Click Yes if UAC asks.
2. Go to:

   HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Preferences

3. On the right, look for a DWORD named FullScreenMode. If it's not there, right-click in the empty space, select New > DWORD (32-bit) Value, and name it FullScreenMode.
4. Double-click it and set the value to 1 (decimal). Click OK.
5. Close regedit and restart Windows Media Player. Try full screen again.

That usually does it. If not, we move on.

Moderate Fix (5 Minutes): Reset the Player's Library Database

This tripped me up the first time too. WMP caches your media library in a local database, and when that gets corrupted—often after a forced shutdown or a large video scan—the full screen toggle breaks. Resetting it clears the junk without losing your files.

1. Close Windows Media Player completely. Check Task Manager to make sure it's not running in the background.
2. Open File Explorer and paste this into the address bar:

   %LOCALAPPDATA%\Microsoft\Media Player

3. Select all files in that folder (Ctrl + A) and delete them. If you get a "file in use" error, restart your computer and try again.
4. Now launch WMP again. It'll rebuild the database from scratch. This may take a minute or two depending on your library size.
5. Test full screen mode. If it works, you're golden.

Skip the other steps if this resolves it. Still stuck? Let's go deeper.

Advanced Fix (15+ Minutes): Re-register WMP Components and System Files

If you've tried the above and the error still shows up, something deeper is broken—probably a missing WMP DLL or a corrupted system file. I've seen this happen on Windows 10 after a major feature update that didn't roll back cleanly. Here's the nuclear option that works every time for me.

Step 1: Re-register Windows Media Player

Open an elevated Command Prompt (right-click Start, select Command Prompt (Admin) or Terminal (Admin)). Run these commands one at a time, pressing Enter after each:

regsvr32 wmp.dll
regsvr32 wmpdxm.dll
regsvr32 wmpui.dll

You should see a success message for each. If any fail, note the error—it'll tell you which file is missing.

Step 2: Run System File Checker

Corrupted system files can cause this too. In the same admin command prompt, type:

sfc /scannow

Wait for it to finish—this takes 5-15 minutes. If it finds and fixes files, restart your PC and test WMP.

Step 3: Reinstall Windows Media Player (Windows 10/11)

WMP is a built-in Windows feature, not a standalone app. To reinstall it:

1. Go to Settings > Apps > Optional Features.
2. Scroll to Media Features (Windows Media Player) and click it. If you don't see it, click Add a feature and search for "Media Features".
3. Click Uninstall. Restart your PC.
4. Go back to Optional Features > Add a feature, search for Media Features, check the box, and click Install.
5. Restart again. Now test full screen.

Still Here? One Last Thing

If none of these worked, the issue might be a conflict with a third-party video codec pack (like K-Lite or CCCP). Try uninstalling those temporarily, then test WMP. If full screen works, you'll need to reinstall the codec pack without the WMP-related options. Or just switch to VLC—it's what I use now.

Short version: registry tweak first, then library reset, then re-register and reinstall. 99% of the time, the registry key fixes it. Good luck!