Fix NS_E_DRM_MUST_REGISTER (0XC00D28A5) in Windows Media

Quick Answer

Delete the DRM folder in %USERPROFILE%\AppData\Local\Microsoft\Windows Media, then restart Windows Media Player. It regenerates the files and registers the client.

Why This Happens

This error means Windows Media Player's DRM (Digital Rights Management) subsystem lost its registration state. Usually happens after a Windows update that partially breaks DRM, or when you copy your user profile to a new machine without bringing the hidden DRM license files. I've seen it most often after the Windows 10 22H2 update and after switching between Windows 10 and 11 builds.

Fix Steps

1. Close Windows Media Player completely. Check Task Manager for any wmplayer.exe processes still running.
2. Open File Explorer. Paste this into the address bar: %USERPROFILE%\AppData\Local\Microsoft\Windows Media
3. Delete everything inside that folder. Not the folder itself — just the subfolders and files. You'll see things like License, DRMStore, Migration. Nuke them all.
4. Restart Windows Media Player. It re-creates those files on startup. That's it — the error should be gone.

Alternative Fix: Registry Tweaks

If the folder reset didn't work (rare, but happens on locked-down corporate machines), hit the registry.

1. Open Regedit as Administrator.
2. Go to HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Preferences
3. Look for a DWORD called DRMState. If it exists, delete it.
4. Also check HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\MediaPlayer\Preferences — same thing, delete DRMState if present.
5. Reboot.

Don't bother with sfc /scannow or DISM here — they never fix DRM registration issues. Waste of time.

Prevention Tip

Before a major Windows update, run this command as admin to back up your DRM licenses:

takeown /f "%USERPROFILE%\AppData\Local\Microsoft\Windows Media" /r /d y
icacls "%USERPROFILE%\AppData\Local\Microsoft\Windows Media" /grant "%USERNAME%":F /t /q

Then copy the folder to a safe place. After the update, paste it back before launching Windows Media Player. Saves you the headache.

One more thing: if you're using Windows Media Center (still a thing in some legacy setups), this error also pops up there. Same fix works.