I have a 256 ram ddr ram in there right now tomorrow im going to buy another 512 ram can i use both 256 and 512 ram cards at the same time my friend told me they both have to be the same number. and also what does it mean when they say pc2700 or pc2100 things like that would it matter which one u buy aslong as you stick to ddr? sorry if its hard to understand.
As you are re-using the old ram, you need to match the speed. Most motherboards will/can run with two different speed ram chips but will only run the whole lot at the lower speed - so there is not much point buying the faster stuff. The numbers refer to the ram speed which is explained here - http://www.kingston.com/newtech/overview.asp
And those sticks of RAM don't have to be the same size, can add as much as your motherboard supports PC2700 is faster than PC2100 and so on.
