I don't think you put 2 modules of different sizes and types next to each other because the stability of your system will be affected. If it starts at all. :) It is important that you have 2 modules of exactly the same type and size, so if you want to keep the old one, buy a 2 gig of the same brand as the old one, but it is still not guaranteed to work. It would be best if you buy 2 modules of 4 pcs, of course I know that the ramams are pretty expensive now.