It's part of your copy of XP... It is called system file checker. Learn
about Xp by taking time to read what came with it and use your browser to
search for info. There is a lot on the Web, that is what 'search' is for. I
have been roundly criticized before for saying this, but having gotten
answers on this newsgroup is one thing, taking the initiative to begin to
help yourself is even better and jumping on a newsgroup and saying 'jeez, i
was just looking for help, not expecting to get a lecture from you' (because
coming here is 'just asking for help') misses the point.
And i bet you don't understand the difference.