My alltime multiple file renaming utility favorite is MultiRen. A freebie from Ziff-Davis Publishing. I like it because I can select specific files, the RtClck on them to rename in any fashion I choose. I've used it in all version of Win from Win95 thru Me, but in XP since SR1, it causes sporadic SHELL32.DLL faults in Explorer when RtClckg (about one time in 45 or 50). Now I only install it for special projects and use Bulk Renamer instead for everyday stuff. If all you want to do is rename extentions, just make a plain text file with the rename command in it (as in Ren *.PZ2 *.HD2) and save it with a name like RenPZ2HD.BAT - copy the file into the folder you want to use it in, and DblClck it. A DOS window will flick into view for a second, and the command will execute. Simplest method I've come up with.