that computer sounds more than fine... you've got over a gig of ram there, u really dont need to waste money on more, and 2.4 ghz processor is fine... id look at some audio tweaks in XP before i shelled out money

i run on half that amount of ram and i run numerous high end VST's, samples, plugins, high end mastering tools etc with not much trouble at all i must say... id recommend taking a look at any cpu saving shortcuts/tweaks in XP and disable any other small programs you have running that ur not using at the same time

im sure there is a website with just XP tweaks on it but for the life of me cant remember its address