Yes. Assuming it uses XP you'll have to get an XP disk. Use that disk to reformat the hard drive and reinstall Windows. Then do what 6string said.

If you don't have an original XP disk or a reinstall disk for your computer (which would include XP) then you'll need either to buy one or get it done for you. If you bring the machine down here then PM me. At home you'll need to take it to a repair shop. The process of reloading Windows, finding and reloading all device drivers (you forgot that, 6string!) and bringing everything up to date as he said, will take upwards of a day. If you take the computer to a shop you'll probably find it uneconomic.

By FAR the best cure is prevention!