And keep in mind, regardless of what has been said above that everything will be fine, that ANY time you mix DRAM from different packages there is no guarantee they will play together, even two packages of the same exact model....That's why DRAM is offered in such a variety of sets, the sticks are tested to work together, if mixing DRAM was as simple as many would have you believe, all the manufacturers would do is sell single sticks and make even more money. That's also why the larger sets I.e. 4 sticks normally cost more than 2 sets of 2 of the same exact sticks, it's much harder to match up four stick that all play together than it is to find 2 that will play nice