I recommend you completely replace and remove the old sticks of RAM. Mixing and matching RAM is never a good idea as it usually leads to instability.
Also, since you seem pretty knowledgeable in the technological department, what's your take on mixing different types of memory? Should I leave my current memory in my system, or should I remove it and just replace it with the new memory? I've heard that it isn't good to mix diff ones and that it can actually have negative effects on your PC. What's your stance on it?
You can try all four modules together as you will have more RAM, but if stability is of utmost importance, I do not recommend it at all.
Edited by james_8970, 20 July 2008 - 07:54 PM.