Hi Schleke,
Information that is stored in the database or the database itself can become corrupted. The Windows Media Player library database can usually recover automatically from database corruption. Here’s how you resolve corrupted library.
1. Exit Windows Media Player.
2. Click Start, click Run, type %LOCALAPPDATA%\Microsoft\Media Player, and then click OK.
3. Select all the files in the folder, and then click Delete on the File menu.
Note You do not have to delete the folders that are in this folder.
4. Restart Windows Media Player.
Note Windows Media Player automatically rebuilds the database.
5. Run Windows Media Player.
If this does not resolve the problem, clear the Windows Media Player database cache files. To do this, follow these steps:
1. Exit Windows Media Player.
2. click Start, click Run, type %LOCALAPPDATA%\Microsoft, and then click OK.
3. Select the Media Player folder, and then click Delete on the File menu.
4. Restart Windows Media Player.
Note Windows Media Player automatically rebuilds the database.
This should fix the issue.
Referred link:
You cannot view, add, or delete items in the library in Windows Media Player 11**http://support.microsoft.com/kb/925718**
Note: The information in the article above is equally applicable for Windows Media player 12.
Regards,
Shinmila H - Microsoft Support
Visit our Microsoft Answers Feedback Forum and let us know what you think.