Fix NS_E_WMP_BSTR_TOO_LONG (0XC00D12F2) in 3 Steps

Quick Fix: Clear the Current Playlist (30 seconds)

I know seeing 0XC00D12F2 pop up is maddening, especially when you just want to play a song. This error usually means Windows Media Player choked on a corrupted playlist entry or a library file that got scrambled.

The fastest fix: clear the current playlist WMP is trying to load.

1. Open Windows Media Player.
2. If you see a playlist on the right pane, right-click it and choose Clear list.
3. Close WMP completely, then reopen it.

If the error disappears, you're done — the corrupt playlist was the culprit. If it returns, move to the next step.

Moderate Fix: Delete and Rebuild the WMP Library (5 minutes)

This is the real fix nine times out of ten. WMP caches your music library in a database that can get clobbered by a sudden crash, a power loss, or even a bad tag on a single MP3 file. I've seen this happen most often after copying a huge folder of music from an external drive.

Here's how to nuke the library safely:

1. Close Windows Media Player completely.
2. Press Windows Key + R, type services.msc, and hit Enter.
3. Find Windows Media Player Network Sharing Service. Right-click it and choose Stop. Leave the services window open.
4. Open File Explorer and paste this path into the address bar (adjust the 7.0 if you're on a newer version like 12.0 — check in WMP Help > About):

%LOCALAPPDATA%\Microsoft\Media Player

5. You'll see files named CurrentDatabase_*.wmdb and possibly Library_*.wmdb. Delete all files in this folder. Don't worry — WMP will recreate them.
6. Go back to the Services window, right-click Windows Media Player Network Sharing Service again, and choose Start.
7. Launch Windows Media Player. It will act like it's the first time — let it scan your monitored folders. This may take a few minutes if you have a big library.

This step clears any corrupted database entries. The error should be gone once the rebuild finishes.

Advanced Fix: Registry Tweak to Force Library Reset (15+ minutes)

If the error persists after a full database wipe, something deeper is stuck — likely a corrupt registry key that WMP keeps referencing. I've only needed this fix twice in six years of support, but it works when nothing else does.

Warning: Editing the registry can mess up your system if you're not careful. Back it up first (File > Export in Regedit).

1. Close WMP.
2. Press Windows Key + R, type regedit, and hit Enter.
3. Navigate to:

HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer\Preferences

4. Look for a DWORD value named LibraryLocation. Right-click it and choose Delete. If it's not there, skip this.
5. Now go to:

HKEY_CURRENT_USER\Software\Microsoft\MediaPlayer

6. Right-click the MediaPlayer key, choose Export to back it up somewhere safe, then delete the entire MediaPlayer key.
7. Close Regedit.
8. Reboot your PC.
9. Open WMP. It will create a fresh, clean registry key and library from scratch.

After the reboot, WMP will ask you to set up your library again. Point it to your music folders and let it scan. The error should be gone for good.

Heads up: Deleting the MediaPlayer registry key will reset all your WMP preferences — visualizations, skin choices, equalizer settings. Write down any customizations you care about before doing this.

Why This Error Happens

The NS_E_WMP_BSTR_TOO_LONG error is WMP's way of saying "the string I read from the database is way too long to be valid." It's almost always a corrupted entry — like a playlist pointing to a file path that got truncated or a tag with an insanely long name. The registry fix is the nuclear option, but 90% of people only need the library delete step.

If you're still seeing the error after all three steps, there's a chance a specific media file is corrupting the library on every scan. Try adding your music folders one at a time to isolate the bad file. But honestly, that's rare — the steps above cover almost every case I've seen.