a good free utility is SPIDER:
http://www.webattack.com/get/spider.shtml
Aside from tracing your url's these files grow and
slow down your browsing. Microsoft then makes more money when you go out and buy an new box.
One other think to keep in mind is that even if you delete
a file on a PC, all or part of the data may still be readable, even after a defrag!
I found a disk wipe utility that overwrites your disk with 27 or 32 passes in a random order. to cleanse old data. If you ever delete a file, the locator or pointer in windows is deleted, but the data remains.
The utility wipes the physical disk by writing and deleting data. Check it out: Eraser