I've read through various questions but don't understand a basic thing about this program. If Eraser is run within XP, does it just delete/erase all non-system files and folders - the files that have private information - and leave XP intact? I'm selling a computer for my father that has just a few files and pictures on it and he can't find the XP install disc. Every topic I've looked at isn't clear to me as to whether the OS is removed and has to be reinstalled.