http://noclone.net/
Features:
True Byte-by-byte comparison , not by CRC / MD5, totally safe to delete files.
Search duplicate file contents regardless of file name
Search duplicate pictures (jpg, gif), video (avi, mpg), songs(mp3), DLLs and any file types
Search files with same contents, same name, zero size and truncated files.
Uhm, vad menas med "Byte-by-byte comparison"? Tar programet bort filer som har exakt samma storlek?