i'd say, add in another 512mb of ram like everyone else has said. then run ccleaner and pc-decrapifier. after that, i'd say run some antimalwarebytes and superantispyware just to be on the safe side. there's really no reason xp should be running very slow once you do all that. unless there is a hardware problem. but it sounds like you just need to clean the cobwebs out and get rid of some windows cruft.