Fix NS_E_DRM_MALFORMED_CONTENT_HEADER (0XC00D279C) Fast

The Problem

You're trying to play a protected media file — maybe an old WMV from a work training video or a Silverlight stream — and instead of content, you get error NS_E_DRM_MALFORMED_CONTENT_HEADER (0XC00D279C). The message says the content header doesn't comply with DRM requirements. Translation: the DRM license data on your machine is corrupted or outdated.

I've seen this most often on Windows 7 and 10 after a Windows Update or when someone copies protected media from a different PC. The culprit here is almost always a stale DRM store in your user profile. Here's how to fix it.

30-Second Fix: Clear the DRM Folder

This resolves 80% of cases. Do this first.

1. Close Windows Media Player and any browser tabs that use Silverlight (IE, Edge in IE mode).
2. Press Windows + R, type %appdata%\Microsoft\DRM, hit Enter.
3. Delete everything inside that DRM folder. Don't delete the folder itself — just its contents. Note: on Windows 10/11, you might see a DRMStore subfolder instead — delete its contents too.
4. Reboot. Then open the media file again. Windows will re-download the DRM license fresh from the server.

Warning: This only deletes cached licenses. It's safe. You're not breaking anything permanently — the license just gets reacquired.

If that didn't work, move to the next step.

5-Minute Fix: Reset Internet Explorer and Re-register DRM Components

This targets the underlying DRM engine that WMP and Silverlight share. IE's reset fixes the hidden settings that store DRM permissions.

1. Open Internet Explorer (not Edge). You might have to search for it in the Start menu — it's still there on Windows 10/11 unless you removed it.
2. Click the gear icon (top right) > Internet Options > Advanced tab.
3. Click Reset. Check Delete personal settings and click Reset again.
4. Restart your PC.

Now re-register the DRM DLLs. Open an admin command prompt:

regsvr32.exe drmclien.dll
regsvr32.exe dsound.dll
regsvr32.exe wmvcore.dll

Run each line separately. You should see a success message for each. Reboot again, then test playback.

15-Minute Fix: Full Clean Reinstall of DRM Components

Skip this unless the first two didn't work. This is for stubborn cases where the DRM store has deep corruption or you're running Windows 7.

1. Uninstall Silverlight (if installed). Go to Control Panel > Programs and Features, find Microsoft Silverlight, uninstall it.
2. Remove all DRM store remnants. In addition to the %appdata%\Microsoft\DRM folder, check %programdata%\Microsoft\DRM and delete its contents too. You'll need admin rights for the %programdata% folder.
3. Reset WMP settings. Open WMP. Press Alt to show menus. Go to Tools > Options > Privacy tab. Click Clear cached DRM licenses.
4. Reinstall Silverlight (if your content needs it). Download the offline installer from Microsoft's archive — don't use the web installer, it often fails on older OS.
5. Run the System File Checker. Open admin command prompt and run sfc /scannow. This repairs any corrupted system files that might be blocking DRM.

After these steps, reboot and test. If it still fails, you're looking at a hardware mismatch or an expired server-side license — which means you need to contact whoever issued the media.

When to Give Up and Do Something Else

If none of these work, the file itself might be damaged or the DRM server is dead. That's common with decade-old Windows Media files from corporate intranets. Two options:

• Convert the file using a tool like HandBrake (if it's not encrypted). HandBrake can strip most DRM headers during re-encode.
• Use a different player. VLC sometimes bypasses DRM checks on older formats. It's not a guarantee, but worth a shot.

Don't waste more than 30 minutes on this — the error tells you the header is malformed, and sometimes that means the source material is simply dead.