I have a HP XT 938 with a Athlon 1300Mhz processor and the RAM is 256 MB. I have a PC100 512 MB card from another HP computer could I run this in my XT 938. If yes can I leave one of the 128 MB cards in place (1-128 slot 1, 1-512 slot 2) I think the mem cards in place are PC 133's. Thanks, Bruce