Fix Windows Media Player Error 0XC00D107C (NS_E_WMPCORE_NOSOURCEURLSTRING)

What's happening

You double-click a music file or video, Windows Media Player opens, and then you get that NS_E_WMPCORE_NOSOURCEURLSTRING error — code 0XC00D107C. The player looks at you like it's your fault. It's not. The file path or URL the player is trying to load is empty, corrupted, or the link itself is dead. Had a client last week whose entire library showed this after a Windows update killed their network shares.

The fix that works 90% of the time

Skip all the registry nonsense you'll find on other sites. Nine times out of ten, this is a simple shortcut or association problem. Here's what to do:

1. Open Windows Media Player (search for it in Start).
2. Press Ctrl+O (Open File).
3. Browse to the file that gave you the error, select it, and click Open.
4. If the file plays normally now, the issue is your file association or shortcut.

Now fix the shortcut: right-click the file that failed, choose Open with > Choose another app, select Windows Media Player, and check Always use this app.

If the file doesn't play even when you manually open it, the file itself is likely corrupted or missing. Check if it's still on your hard drive or if a network share went offline.

Why this works

Windows Media Player stores a list of recent files and playlists in a cache — that's the .wmdb database file. When a file is moved, renamed, or the network path changes, that cache still points to the old location. The player gets a blank URL because it can't resolve the path. Opening the file manually bypasses the cache and forces the player to look at the actual file location. Re-associating the file type ensures the correct handler is used next time.

When the above doesn't work

Sometimes the error sticks around because the cache itself is corrupted. Here's the nuclear option:

1. Close Windows Media Player completely.
2. Open File Explorer and paste this into the address bar: %LOCALAPPDATA%\Microsoft\Media Player
3. Select all files in that folder (press Ctrl+A) and delete them. Yes, all of them.
4. Restart Windows Media Player — it will rebuild the cache.

Don't worry — this doesn't delete your music. It only wipes the player's library database, playlists, and sync history. You'll need to re-add your music folders (File > Add to Library), but it's fast.

Less common variations of the same issue

Streaming URLs (radio stations, podcasts): If you get this error when trying to open a URL (like an .asx or .pls file), the link itself is probably dead or malformed. Open the file in Notepad — if you see <REF HREF="" /> with nothing between the quotes, the provider messed up. Find a new link.

Corrupted registry key: Rare, but possible. If you've tried everything and the error persists, a registry entry might be stuck. But I'd only go here if you're comfortable. Open Regedit and navigate to HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Player\RecentFileList. Delete the entries inside — this clears the recent files list without nuking the whole cache. Test Media Player afterward.

Third-party codec packs: I've seen K-Lite Codec Pack cause this on Windows 10 version 22H2. The codec overrides the player's built-in handling. Uninstall the codec pack, test Media Player, then reinstall a stripped-down version (like the Basic option in K-Lite) if you really need it.

Preventing it from coming back

• Don't move files around after adding them to your library. Media Player tracks them by path. If you move a folder, use Organize > Manage libraries in the player to update the watched folder.
• Avoid using mapped network drives for your media library. Drive letters can change. Use UNC paths like \\server\share\music instead.
• Run Media Player as administrator once after a major Windows update — this resets permissions on the cache folder and prevents the database from corrupting.

And honestly? If you're still dealing with this error and you don't need Windows Media Player for anything specific, switch to VLC. It's free, handles everything, and never gives you NS_E errors. But if you're stuck with WMP for work or legacy reasons, these steps will get you back up in five minutes.