DupKiller is the fastest and the most powerful tool for searching and removing duplicate files. The program will find unneeded copies of files in those locations where you even would not consider to search. There is comparison not only by name, last modification date or size. One can compare files by their contents, and what's more, to set what per cent they must match; one can search different-length files, include or exclude files by mask, etc. A lot of scan options helps flexibly customize your search. In addition, unlike another programs of this sort, DupKiller performs all operations faster and better, because of complicated algorithms of data processing built in the search mechanism of the program.
Software that can be used as an alternative to DupKiller: