Yes you probaly would need a new powersuppply for the 6600, but the 6600's are in agp 8x and you only have a 4x slot so it will run slower than it's fastest speed. you might be better off getting a new mobo and proc though, but we can try to make this work. I say buy an other 512mb ram, a geforce 6600 and you should be alright on maybe low settings because of your proc. and you videocard in a 4x slot.