I would say either upgrade the hard drive or the processor. If you are low on cash than go for the hard drive. Get about 80+ gigs of space since games are taking up more and more memory. If you decide to upgrade the processor than chances are you are going to need to upgrade the motherboard too. But when you do get the money, go AMD athlon XP or Athlon 64. In my opinion, those are 2 of the best processors out there.