Something else I just thought of that might be useful is a program called deepfreeze.
It cost about $25, but it would be well worth it if you don't plan to do anything else on that comp. Basically, it makes a copy of your computer after you install it. Then, every time you shut down your computer, it reverts back to this copy. There for, there is no need for virus scans, spyware protechtion, or anything like that. Really nifty, but you CAN NOT save anything on the computer without disabling the prog and restarting the computer.
Just a little side note I thought I might throw in. That comp wouldn't do too bad with virus scans and all, but this would keep it for slowing down...