Hi, i been running on 2 gigs of corsair ddr2 pc6400 ram for a year, i decided to buy an extra 2 gigs of ram but theyre G.skill brand ddr2 pc6400, my question is that im running windows xp. Am i even gonna see a difference, does xp utilize over 2 gigs? Or do i need to upgrade to windows vista to hold the advantage? thanks, reason i upgraded is because i also upgraded my graphic card from a x1900xt to a 8800gt. Does 4 gigs substantially help with power hungry games like crysis? Thanks alot !