Fix NS_E_DRM_KEY_ERROR 0XC00D2721 on Windows Media Player

You're stuck with a DRM error that kills playback of protected media

You try to play a WMA or WMV file you legitimately bought, and Windows Media Player throws up 0XC00D2721 (NS_E_DRM_KEY_ERROR). The player won't play the file, and you're staring at a nonsensical hex code. The cause is almost always a corrupted DRM license store. Here's how to fix it, no registry hacking required.

The fix: delete the DRM folder

1. Close Windows Media Player and any Silverlight-based apps (like old Netflix in a browser).
2. Press Win + R, type %USERPROFILE%\AppData\Local\Microsoft\, and hit Enter.
3. Look for a folder named DRM. Right-click it and delete it. You'll need admin permissions – click Yes if UAC asks.
4. Now open Windows Media Player. It'll rebuild that DRM folder from scratch with fresh license data.
5. Try playing the file again. It should prompt you to acquire the license online. Say yes, and it'll authenticate fresh.

That's it. 9 out of 10 times this wipes the error. The reason step 3 works is that the DRM folder holds the encrypted license store file drmstore.hds. When that file gets partially written or corrupted (happens after a crash, sleep/resume, or disk full), Windows Media Player can't parse its own license table. Deleting the whole folder forces a clean rebuild the next time you play protected content.

Why the error actually happens

The DRM subsystem in Windows (built on the old Windows Media DRM v9/v10 stack) writes license keys to a local store. Each license is tied to your machine's hardware hash. If the store gets corrupted – say from a sudden power loss while the player was writing a license – the key lookup fails. The error code 0XC00D2721 means "DRM key is invalid or missing from the store." The player sees no valid key, so it refuses to decrypt the file. The fix isn't about the file itself; it's about the broken index on your machine.

Less common variations and edge cases

Silverlight-based apps (old Netflix, Amazon Prime, Hulu)

If the error appears in a Silverlight app (browser-based), the same fix applies. Silverlight shares the same DRM store with Windows Media Player. But you also need to clear Silverlight's app cache: in Internet Explorer, go to Tools > Internet Options > Settings under Browsing history > Delete > tick Temporary Internet Files and Cookies. Then restart the browser. Silverlight will re-download the DRM component.

Windows 11 or 10 with Protected Media Playback disabled

Rare, but check: go to Settings > Apps > Video playback and make sure "Automatically process video to enhance it" is on. Some users disable this for performance, and it can interfere with DRM. Turn it back on and retry.

Corrupt Windows Media Player database

If deleting the DRM folder fails, the media library itself might be corrupt. Close the player, go to %USERPROFILE%\AppData\Local\Microsoft\Media Player, and delete everything inside (but not the folder itself). Reopen the player – it'll rebuild the library. This is overkill if the DRM fix worked, but try it as a last resort.

File is actually from a different account or machine

If you transferred a protected file from another PC or user account, the license won't match. DRM licenses are machine-specific. You need to re-download the file from the original store (Amazon, iTunes, etc.) with your current account logged in. Deleting the DRM folder won't help here – you need the new license.

Prevention: avoiding this error going forward

• Don't kill Windows Media Player mid-playback. Use Task Manager only when frozen. Hard kills can corrupt the license store during write.
• Avoid disk-full scenarios. If your system drive runs out of space while the license store is writing, you're asking for corruption. Keep at least 5% free.
• Backup your DRM folder if you have many purchased files. Copy %USERPROFILE%\AppData\Local\Microsoft\DRM to another location. If it corrupts later, restore it instead of re-downloading everything.
• Use modern players. If you can, convert old WMA/WMV files to MP4/M4A using a tool like HandBrake. DRM-free files never hit this error. Of course, that means stripping DRM legally – only do this for files you own with no resale intent.

One more thing: if you're on Windows 10 22H2 or Windows 11 23H2, Microsoft deprecated the old Windows Media DRM in some security updates. The error might actually be a compatibility warning. In that case, use VLC media player or MPC-HC with the appropriate codecs – they skip DRM verification for local files and often play corrupted stores just fine. But that's a workaround, not a fix.