I'm trying to upgrade an older amd athlon computer for my wife. I am running 2- 256mb sticks of ram one stick is pc 2100 and the other is pc 2700. I want to get a stick of 512 but i'm not sure if i should get pc 2700 or pc 3200? And should i keep in the pc 2100 stick or take it out? I am also upgrading her motherboard and getting a new cpu and video card. Any help would be great! Thanks