noobz question here.....

i try google but it get more confusing so hope lyn member can help

i using asus p5rd1-vm motherboard

now the ram i got is 256 ddr400 kingston,,,plan to upgrade the ram to 2gb or highest possible.....what kind of ram shud i buy?

ddr400? or ddr2?

reli noob plz dun flame

thanks