ok, you have to have two of the same sticks of RAM to run dual channel mode, but you don't necessarily have to purchase them in a dual channel memory kit. its just more of a guarantee that they will work in dual channel mode if you buy them that way. if you don't pruchase ram in a kit, just make sure you order two of the same sticks. for instance, you can't use a 256MB and a 512MB together and expect them to run in dual channel mode. some other things they must have in common besides size is clock speed, type of chips it they use, and type (double-sided or single-sided).