When I have experienced this error installing XP it has usually turned out to be caused by a scratched XP CD or a dirty or defective CD Drive. Inspect your disc for scratches and/or smudges. You can clean a CD by wiping it with a lint free cloth from the centre hole out to the outer edge in straight lines (do not polish in circular motion). Also, you can try a CD Drive Cleaning Disc that you should be able to purchase at your local computer store or office supply store.
Those are the two most common reasons for your stated problem, but other reasons may include defective system RAM and /or failing hard disk drive.
A clue might be found in the reason why you need too repair your XP in the first place.