Here's a freeware one http://personal.inet.fi/business/toniarts/ecleane.htm but I would be very cautious of deleting duplicates. Many programs have a registry pointer to a particular folder for it's file and will throw up a wobbly if it can't find it.
here is a gr8 program which i use to remove copies of same file from my system
u can have it here
its a freeware and can be downloaded from here....DOUBLE KILLER