Exactly what hefe said.. u need a new psu for a better GPU to power it
Pci-E ---- Pci Express slots. There on your motherboard google the model of ur computer and see if it has atleast 1 of these slots.
Hmm sorry didn't refresh the page.. so now we need some ram..tell us if ur OS - Operating System (windows vista, windows XP , etc.)
Then if it's 32 bit or 64 bit.
And, if you want 2gb of ram then pretty much your fine with any of the two ( 32 bit, 64 bit) That's what I currently have.