I have big lagg on 2 games (one on the internet and one off)?

Ok i have a dell dimension 4600 2.80 ghz processor 1g of ram a nvidia gforce fx 5200 and its on WINDOWS XP and my friends is a dell dimension 4600 512 mb of ram and nvidia gforce fx 4600 and 2.4ghz(WINDOWS XP). His computer has absolutley no lagg at all and we have all the same stuff. we even set our game setting the igsact same. we both have the same high speed wireless dsl internet. Why would a worse computer run more than twice as smooth than a better one? I even turned off every program but the games and the did not work. The games are gunz online and stronghold legends. I have way above the requirements and it doesnt work someone think of wat the problem could be