Just look at the spec. for the 8800GTX ,it say it need a power supply of 450 watt mimimum . You are running it kind of close with that power supply[ 500 watt],I would go with a 550 to 600 watt power supply. If you run more then 1 harddrives or are going to run a second card I would go with a even higher watt power supply. I read somewhere that those card like a lot of power. I would not go cheap on a power supply with a 600.00 dollar card,I would wait and save up some more money and buy a good power supply.