uhm i'm guessing that you mean Ram.? not Rimm?

either way then you can do that, just make sure that the stick of ram are of the right sort for your type of motherboard.

?Usually they have pc133 etc on the stick of ram.
So just check with the sticks that you already have, and see if you can spot there frequency and then go into the shop and get the ram with the same frequency.

Someone might be able to offer more detail, as i am to tired to really think at the moment yaaawn.
f2B