further to the above two posts, before booting up into safe mode, switch OFF system restore then reboot into safe mode.
Apparently certain files are flagged to windows XP as essential files, and windows will restore them automatically if you delete them.
TBH i dont know how true the above is, it may be myth, but from experience removing stuff like this ive found instances where it was only possible to do it with restore turned off. (in all honesty ive never had that crap be any use anyway. is always off now.)
if you run "hijack this" and post the log it could also help provide clues as to whats on your system too.