hello, ive been surfing the web looking for this asnwer but i can only seem to find the oposite answer, everything says u cant put ddr2 ram on a motherboard used to run ddr ram. and thats great, but what IM wondering is the oposite, see i am buying a new dell e521 and it takes ddr2 ram, but i have 2 ddr 512mb ram sticks from my old computer. can i put these on the ddr2 mother board or do i HAVE to have ddr2 ram?...