This worked in Vista for me..
Because I always migrate and copy files / folders from one OS to another when I upgrade Windows, and as my housekeeping isn’t as good as it should be, I reckon I have 100’s of Gigs wasted in duplicate files..
So I downloaded the application called duplicate file finder – http://www.snapfiles.com/download/dldupfilefinder.html
Added in my paths, and started it going.. I have 4 hard drives I wanted to scan 2 x 250Gig and 2 x 80Gig. It took a while, but when it had finished I had a nice list of duplicates where I could either just remove all (which I didnt as there were lots of system files I didnt want to delete) or pick the ones to remove.
Saved me lots of Gig 🙂
WARNING: Be carefull with this, if you are not sure about what you are deleting you might remove some critical system files.