CompROM .. Compairs Images. I've tested this with both Coleco, GameBoy
and Atari 2600 images. The syntax is fairly simple.

Comprom [IMAGE FILTER] [BYTES TO READ]

The image filter works just like dir.. *.ROM or *.GB or R*.*. Bytes to
read is optional. Defaults to 350 byteread. You can specify up to 10000
bytes to read. Output is a batch file called 'results.bat'. I've found
this utility very handy for weeding out all my duplicate images.