Originally Posted by celegorm
pc 400 is ddr. 533 is ddr2. they will not work in the same motherboard.
not correct. there is ddr400, then there is ddr2-400. Then there is ddr533, and surprise surprise, ddr2-533.
As long as both are the same (ddr or ddr2) they will work fine. Only thing is that both of them will be working at 400mhz because thats the speed of the slower one. And no, if for some reason it wouldn't be compatible it shouldn't harm your pc in any way.