If you’ve been experiencing the problem where you can’t add files to Windows Media Player’s library no matter what you do, then you probably have a corrupted database, and you’ll need to delete it and then re-add all of your media to the library.
NOTE: These steps will delete files, so you should make a backup of any of these files before you do this, especially if you have purchased music via one of the online music shops. Your music will not be deleted, just the database.
The first thing you’ll need to do is go to Control Panel \ Administrative Tools \ Services for XP and look for the services that start with “Windows Media Player”. (Make sure Media Player is closed too)
Click the stop button for each and make sure that all of the services that start with “Windows Media Player” are stopped before you continue. Next, open up an explorer window and paste in the following path into the address bar.
%USERPROFILE%\Local Settings\Application Data\Microsoft\Media Player\
You’ll see a bunch of files in the folder. I’d advise moving all of these files to another directory somewhere else, but you could also delete them if you were daring enough.
Now when you restart Windows Media Player, you should be able to add music to your library again.