/Music/iTunes there are three files from the iTunes Library (iTunes Library, iTunes Library Extras.itdb, and iTunes Library Genius.itdb), they keep all the library structure of your musics. Once you delete them, it will clean your iTunes and it will start a new library from scratch.
If you plan to re-install your iTunes (which I don't think it is necessary), please don't forget to delete the following preferences:
* com.apple.iTunes.eq.plist
* com.apple.iTunes.helper.plist
* com.apple.iTunes.plist
* com.apple.iTunesHelper.plist
You will simply have to add the musics back to your iTunes. I recommend you to add like 10 musics and check if it worked (it will probably work). After that you can add your remaining library. Hope the solution now gets more clear to you.
P.S. Cait deleted everything, it was not a recommendation, she/he simply did it...