Just pop in the original XP disk, reformat your hard drive, and reinstall. If there is anything you want to save, make sure you back up to an external hard drive because everything will be wiped with the reinstall.
This is a h/p computer about 6 years old lap top with windows xp home.
It has gotten so slow would like to start over not in need of keeping
any programs or things I have put on machine. Just bring back to when new. then I will start over.