d'peg! will allow you to scour any number of harddrives and folders, even removable media drives like CDRom and Zip drives with disk swap prompting, snarfing out duplicate graphics files using traditional methods of Name, Size, Checksum, & CRC, fuzzy modes of Color Content, and intelligent modes of Tolerant Pattern Matching with Dynamic AutoCropping - to catch duplicates that have been color adjusted, resized, resaved in any of 29 graphic file formats - even bordered, Spam text'd, and flipped or rotated!

http://www.somewareonthe.net/dpeg.htm