i have heard about something called a system file check that kinda does like a repair doesnt fix anything... ive never used it before because i would rather go on and do the whole repair... here is the link
http://ask-leo.com/what_is_the_syste..._i_run_it.html it will explain what it is and how to use it... and if it were me i would just go to a torrent site and grab me a copy of what ever you had, or go to your local computer store with 5 bucks and tell them you would like a copy of your distro(if they had any sense they would trade 5 bucks for a burnt copy of xp)