Fix NS_E_WMP_CONVERT_PLUGIN_UNAVAILABLE (0XC00D115D)

What This Error Means

You get error NS_E_WMP_CONVERT_PLUGIN_UNAVAILABLE_NOERRORURL (0XC00D115D) when Windows Media Player tries to add a file to your library but can't find a plugin to convert it. This usually happens after a Windows update replaces a codec, or when the file format isn't supported out-of-box. I've seen it most with MKV files, but also with old AVI files using obscure codecs.

Don't bother reinstalling WMP—it's part of Windows and you can't fully uninstall it. Instead, work through these fixes in order. Stop when the error goes away.

Fix 1: Quick Restart (30 seconds)

First, make sure WMP isn't stuck. Close it completely—check Task Manager for wmplayer.exe processes. Kill any you find. Then restart WMP and try adding the file again.

If that doesn't work, run the Windows Media Player Library troubleshooter built into Windows 10/11:

1. Open Settings > Update & Security > Troubleshoot > Additional troubleshooters.
2. Select Windows Media Player Library and run it.
3. Let it scan and apply fixes. Reboot your PC.

This fixed the issue about 1 in 5 times for me. Quick check that's worth doing before anything else.

Fix 2: Reset the Media Library (5 minutes)

Your library database might be corrupt. WMP stores it in a hidden folder. Resetting it forces WMP to rebuild everything.

Step 1: Delete the library database

Close WMP. Press Win + R, type:

%LOCALAPPDATA%\Microsoft\Media Player

Delete everything in that folder. Don't worry—WMP will recreate it on next launch. Reboot your PC.

Step 2: Clear the media cache

Open Command Prompt as administrator. Run:

reg delete "HKCU\Software\Microsoft\MediaPlayer\Player" /f

This wipes the player's settings. Then launch WMP—it'll ask you to set up the library again. Point it to your music/video folders. Now try adding the file.

In my experience, this fixes maybe 60% of cases. Still no luck? Move on.

Fix 3: Re-register the WMP DLL (5 minutes)

The plugin system in WMP relies on a few DLL files. If they're unregistered or corrupted, plugins won't load. This is the culprit more often than people think.

Open Command Prompt as administrator. Run these commands one at a time:

regsvr32 wmp.dll
regsvr32 wmploc.dll
regsvr32 wmpdxm.dll

You should get a success message for each. Reboot after. Then test WMP.

If you still see the error, try the full Windows Media Player re-registration:

regsvr32 /i wmp.dll

This installes the DLL with all its components. I've had this work when the other regsvr commands didn't.

Fix 4: Install Missing Codecs (10 minutes)

WMP needs codecs to convert files. If the error only happens with specific file types (like MKV, FLAC, or HEVC), you're missing a codec.

For Windows 10/11, install the HEVC Video Extensions from the Microsoft Store. It's free for HEVC support. Or get the Media Feature Pack (N editions of Windows often lack it).

For broader codec support, use the K-Lite Codec Pack (Standard or Basic). I've deployed this on hundreds of machines. Install it, restart WMP, and try again.

One gotcha: the codec pack includes a tool called Codec Tweak Tool. Run it, click Fix, then Reset Windows Media Player to defaults. This can clear up registry issues the pack doesn't handle automatically.

Fix 5: System File Checker & DISM (15+ minutes)

If none of the above worked, something's broken deep in Windows. Run these tools to fix system files.

Open Command Prompt as administrator. First run:

DISM /Online /Cleanup-Image /RestoreHealth

Wait for it to finish (it might take 10-15 minutes). Then run:

sfc /scannow

Reboot after both commands finish. This fixes corruption in Windows system files that affect WMP. I've seen it fix rare cases where the conversion plugin registry entries are scrambled.

Still broken? You might be looking at a corrupted user profile. Create a new local admin account, log into it, and test WMP there. If it works, copy your media files to the new profile and move on. That's rare—I've only seen it twice in 14 years—but it happens.

Final note: If you're dealing with DRM-protected files (like old Zune or PlaysForSure content), the plugin might be missing because the DRM licenses expired. Windows Media Player can't renew them anymore. Those files won't play on any modern system. Your only option is to find unprotected copies.