Fix NS_E_DRM_LICENSE_NOTRUSTEDCODEC 0xC00D280D in Windows Media Player

You're watching a rented movie or a DRM-protected video file in Windows Media Player (WMP) and suddenly it stops. Instead of playback, you get a popup with NS_E_DRM_LICENSE_NOTRUSTEDCODEC and a hex code 0xC00D280D. This typically shows up right after a Windows update, or after installing a newer version of a codec pack (like K-Lite), or when you try to play a file that was encoded with a codec that your current DRM system doesn't recognize as safe. I've seen it happen on Windows 10 21H2 and Windows 11 23H2, but it's not version-specific.

What's actually happening here is a security check failing. DRM (Digital Rights Management) in Windows Media Player doesn't just trust any codec. It keeps a list of codecs it considers "trusted" for playing protected content. When the codec identifier or its version doesn't match what the DRM system expects, it refuses to decode the video. The error literally translates to "the license says the codec is not trusted." It's a safeguard against malicious codecs that could steal decryption keys, but sometimes it blocks legitimate codecs because a certificate expired or the codec got updated without re-signing.

Most people think they need to download a new codec or reinstall the player. That's wrong. The real problem is usually corrupt DRM data or a broken codec signature check. Before you spend hours hunting for a codec, try the fixes below. They're ordered from simplest to most thorough.

Fix 1: Reset the DRM store

The easiest fix is to clear the local DRM files and let Windows re-download them. This resets the trust list. It's safe because it doesn't touch your media files. Here's how:

1. Close Windows Media Player completely.
2. Press Win + R, type cmd, and press Ctrl+Shift+Enter to run Command Prompt as Administrator.
3. Type the following and press Enter:
   

   cd /d %windir%\ServiceProfiles\LocalService\AppData\Local\DRM

4. Delete everything in that folder. You can type del *.* /f /q or open the folder in Explorer and select all, delete.
5. Restart your computer. Windows will recreate the DRM files on the next use of WMP.

The reason this works is that the error is often caused by a corrupted drmstore.hds file. That file holds the license store and the trust list. Deleting it forces Windows to regenerate it from the system's built-in certificates. You might have to re-download licenses for previously purchased content, but that's a minor trade-off.

Fix 2: Re-register the Windows Media Player DLLs

If resetting DRM didn't help, the next suspect is a broken registration of the codec-related DLLs. Windows updates sometimes leave orphaned registrations. Re-registering them takes about a minute:

1. Open Command Prompt as Administrator (same as above).
2. Type these commands one by one, pressing Enter after each:

regsvr32.exe /u wmpeffects.dll
regsvr32.exe wmpeffects.dll
regsvr32.exe wmvdspa.dll
regsvr32.exe wmadmod.dll
regsvr32.exe wmvcore.dll
regsvr32.exe mp3dmod.dll

After each command, you should see a success dialog. Then restart your computer and test playback.

What's going on here is that those DLLs are the actual Windows Media codec modules. The error NOTRUSTEDCODEC basically means the DRM layer can't verify the signature of one of these DLLs. Re-registering them validates their file paths in the registry. If the registration is broken, the trust check fails even though the codec itself is fine.

Fix 3: Check for conflicting third-party codecs

If you have K-Lite Codec Pack, CCCP, or any similar pack installed, they often include their own versions of the Windows Media codecs. That's a classic source of this error. The DRM system sees a different file version and flags it as untrusted.

Uninstall the codec pack completely, then restart. Don't reinstall unless you absolutely need it. For most modern video formats, WMP on Windows 10/11 handles them natively with the Media Feature Pack. The only reason to have a third-party pack is for old formats like DivX 3 or AC3 audio, and even then you can use a dedicated player like VLC instead of messing with WMP.

Fix 4: Run the Windows Media Player Troubleshooter

This might sound generic, but the built-in troubleshooter is actually good at finding invalid DRM files. It won't fix registry issues, but it catches file permission problems. Go to Settings > Update & Security > Troubleshoot > Additional troubleshooters and select Windows Media Player. Run it. It'll scan and offer to reset DRM if it finds corruption.

If it still fails

When none of the above work, the problem is likely a stale certificate in the DRM trust chain. The real fix is to force Windows to refresh its media feature support. Here's what I'd do:

1. Open Command Prompt as Administrator and run sfc /scannow to check system file integrity. This catches corrupted codec files.
2. If SFC reports issues, run DISM /Online /Cleanup-Image /RestoreHealth.
3. If the error persists after that, you might have a driver issue with your graphics card. The video decoder uses GPU acceleration, and a faulty driver can cause the trust check to fail. Update your GPU driver from the manufacturer's site (NVIDIA or AMD) rather than relying solely on Windows Update.

The last resort is to use a different media player. Windows Media Player is ancient and its DRM stack is fragile. VLC doesn't support DRM-protected files, but for locally stored unprotected videos, it works perfectly. For DRM content, you should really use the official app for that store (like Movies & TV from Microsoft Store). But if you're stuck with WMP for work reasons, the fixes above solve 95% of the cases.

One more thing: if you're playing a file you downloaded that has DRM, check the file extension. Some files are mislabeled. A real DRM file will have a .wmv or .wma extension and usually has a license header. If it's a regular MP4 that's throwing this error, it's almost certainly a codec conflict—skip the DRM fixes and go straight to uninstalling codec packs.