ITunes 10 Update

[T&S]

I've just updated my ITunes to V10. On rebooting, it asked me if I wanted ITunes to organise my files, to which I answered yes. When ITunes opens up, I now have a duplicate of every song in my library, although the ITUnes folder on my Hard Drive still has half that. Is there a way I can delete duplicate files from the library as they don't appear to be on myHard Drive anyway.

TIA