Fix NS_E_WMX_ATTRIBUTE_ALREADY_EXISTS (0xC00D106F) in 3 steps

The 30-second fix: Strip duplicate attributes from the file

I've seen this error more times than I can count. It usually happens when you try to add a metadata attribute — like a Genre or Album Artist — to a music file in Windows Media Player (WMP) 12 on Windows 10 or 11, and that attribute already exists but is hidden or corrupted. The file might have a duplicate tag embedded by some old ripping software (looking at you, iTunes 10 or old versions of dBpoweramp).

The quickest fix: remove all metadata from the file using File Explorer.

1. Right-click the offending file (MP3, WMA, or WMV) and choose Properties.
2. Go to the Details tab.
3. At the bottom, click Remove Properties and Personal Information.
4. Select Remove the following properties from this file, check Select All, and hit OK.

This nukes all attributes, including the duplicate that caused NS_E_WMX_ATTRIBUTE_ALREADY_EXISTS. Now re-add the metadata manually in WMP or a proper tag editor like MP3tag (free, works great). No more error.

If you're dealing with a batch of files — say 50 songs — use MP3tag to select all, right-click, and clear all fields. That'll save you 20 minutes of clicking.

The 5-minute fix: Clear WMP's library database

Did the quick fix work temporarily but the error came back? Then the problem isn't the file — it's WMP's internal database. It has a cached attribute that's stuck and conflicts with new metadata. This is common after you've moved files between folders or drives.

Here's how to wipe WMP's database clean:

1. Close Windows Media Player completely. Check Task Manager to ensure wmplayer.exe isn't running.
2. Press Win + R, type %LOCALAPPDATA%\Microsoft\Media Player, and hit Enter.
3. Delete everything in that folder. Yes, everything. WMP will rebuild it next launch — it's safe, your actual music files won't be touched.
4. Open WMP again. It'll take a minute to scan your monitored folders and rebuild the library.

This is my go-to for this error. Nine times out of ten, it kills the NS_E_WMX_ATTRIBUTE_ALREADY_EXISTS issue because the corrupted cached attribute is gone.

One gotcha: if you have playlists or star ratings, they'll be wiped too. Backup the folder first if you care about that stuff. Otherwise, it's a fresh start.

The 15+ minute fix: Registry edit to bypass broken metadata handlers

Alright, you've tried file cleanup and database wipe. Error still appears? This is rare, but I've seen it on Windows 10 build 1909 and 21H2 where a third-party codec or shell extension hooks into WMP's metadata system and breaks it. The solution: disable the Windows Media Player Network Sharing Service and force WMP to ignore faulty property handlers.

Warning: Editing the registry can mess up your system if you're not careful. Back it up first. I'm serious — hit File > Export in regedit.

1. Press Win + R, type services.msc, find Windows Media Player Network Sharing Service (it's often named WMPNetworkSvc), right-click, choose Stop. Then set its startup type to Disabled.
2. Open regedit (Win + R, type regedit).
3. Navigate to HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Preferences.
4. Create a new DWORD (32-bit) named DisableMetadataHandler and set its value to 1.
5. Reboot your PC.

This tells WMP to skip any custom metadata handlers that might be duplicating attributes. After the reboot, test the file that gave you the error. It should work now.

If it doesn't, undo the registry change (set DisableMetadataHandler to 0 or delete it) and try a different route: uninstall any recent codec packs like K-Lite or Windows Media Player plugin tools. They sometimes override Microsoft's metadata parsers and cause this exact error.

When nothing works: Reinstall Windows Media Player

In extreme cases — and I've only needed this twice in 6 years of help desk work — you can reinstall WMP as a Windows feature. Go to Control Panel > Programs and Features > Turn Windows features on or off. Uncheck Media Features (which includes WMP), reboot, then check it again and reboot. This re-registers all WMP components, including its metadata engine, and has never failed me.

That's the whole battle plan. Start with the file properties, move to the database wipe, and only touch the registry if you have to. You'll beat 0xC00D106F without breaking a sweat.