I am confused as to which files to delete. I have found NO information about the subject that ANSWERS my problem, which is this. If I have a lot of duplicate FILE to delete, should I delete ALL but one of each group of duplicate files or do I need to keep 1 of them each for each
 program that uses the particular file.Will a program find its file, where ever it is, or is it possible for 2 programs to USE the 1 file at the same time.If not, how will I know which program needs a copy of the file saving? Why delete any?Do they not take up room and slow the PC down a tad? It seems a handful of folk have written programs to do just that ( clear up duplicate files in order to speed up the PC ).Unless your hard drive is small or very low on space, duplicate files neither slow down anything nor need to be deleted.And to add to Allans comments ...removing them generally will cause havoc...Especially since Vista and 7 (not so in XP) keep a plenty of system file backups in several different locations.
Very handy, when some system file(s) get corrupted.Additionally, some "duplicates" aren't duplicates at all, but hard-links to the same files; this is especially true with the various junctions/folder hard-links in later windows versions.