Yea it's DDR2 that's just laziness on my part because DDR2 slots are different. I get that the lower speed will be all I get out of a faster ram to match up, but the expense was only $21 per gig anyway and they didn't have any 533MHz 4200's hence the 5400's that were supposed to be compatible. I think I will just shoot for a Win 7 upgrade and see how it goes.