Originally Posted by
powderbanks i would just backup all your important data and reinstall xp (or linux). depending on what you're using your computer for, i'd go to ubuntu. i had it on my laptop (the harddrive just died..i think. rootbrian do you know a lot about ubuntu?) and an older desktop before and i liked it a lot. and it runs very well on older/slower machines.
when you reinstall xp (or whatever os you get) there is an option/you are forced to reformat your hard drive. after windows is done doing its thing, do a windows update asap. or if you feel comfortable enough, you could slipstream sp3 and any other updates/drivers to a new installation disk. after that's all done, install malwarebytes, spybot s&d and an antivirus. i like avg free.
if you're really set on keeping this computer, have you thought about buying some more ram, if it's not already maxed out?