does anyone know of a program that will restore windows to its full working order after a file has been deleted ,i've tried system mechanic,reg mechanicand a few others but nothing seems to work ,currently running windows xp pro with service pack 3
Depends which file has been deleted. You could try a "Repair" installation if you have a valid XP disk and license key. (Google for: XP repair install).
I would strongly advise that you back up as much as possible before trying this. It can be a bit scary (hence not giving full instructions here) but isn't that hard to do. Usually takes an hour or so. Once done, you will need to install all Service Packs and updates issued since your disk.