Ian Cunningham said:I've not had any experience with this sort of software, however this one seems to get the thunbs up - and is free
http://www.download.com/Duplicate-Cleaner/3000-2248_4-10584403.html
Ian Cunningham said:I'd be very careful running things like this - I'd only suggest using it to check you haven't doubled up on music files... when it comes to any system files I'd leave them alone