temp files…just empty temp folders.
http://www.geekstogo.com/forum/files/file/187-tfc-temp-file-cleaner-by-oldtimer/
anyway i dont see the problem with some fragmented files… and there will always be some as they move/accessed http://lifehacker.com/5976424/what-is-defragging-and-do-i-need-to-do-it-to-my-computer