if you want to clean everything in your harddrive and loose all the data,
why dont you just boot it from the XP CD. and go from there.
if your windows is corrupted and you dont want to loose the data on the drive,
boot it from CD and choose install.
setup will find that there is a windows installed on the machine and will ask you if you want a clean install or you want to repair.
choose repair and have your CD KEY ready.
this way you MAY loose very little information and have windows repaired.