Here are a few tips and techniques on how to get rid of duplicate songs in your iTunes Library as well as some precautions you should take before deleting duplicate tracks.
How To Delete Duplicate Movies and Music in iTunes
As your iTunes Library grows, you will probably lose track of exactly what music you have already imported and end up with duplicate songs and video files. You might accidentally import a CD twice or add files from BitTorrent. Or maybe a friend with a big Terabyte hard drive "loaded you up" with a lot of music recently.