i have a p4 3.0 cpu w/ asrock 77i65g mobo. i have also 1 512mb pc400 ddr1 and 256mb pc400 ddr1 memory in that unit, which means a total of 768mb.can i put ddr2 or ddr3 1gb ram in my unit?can you give me your answer if you dont mind.thanks a lot.i'm hoping to your answer and it will mean a lot.