iTunes De-Dupulator is a desktop app that allows you to remove duplicates from your iTunes library on Windows.
iTunes has a built-in duplicate detector which is somewhat aggressive. It detects duplicates based only on the artist and song. De-dupulator takes into account more aspects of the song and presents them in table where you can preview them before removing dulicates.
De-Dupulator looks at the length of each song to determine if the songs are actually different. This happens with live versions of a song, remixes, alternate versions, etc. iTunes de-dup feature will think that the live version is a duplicate because it has the same artist + song name. Don't delete those rare live imports!
De-Dupulator does not automatically select songs for deletion if they are part of a different album. For example, you may have one song that is on an album. But that same song is also part of a compilation. Although the song is technically a duplicate, when you delete it one of your albums will now be incomplete. In this case you may wish to keep both versions so that your albums remain in-tact.