I have a laptop that runs Windows Vista 32bit operating system. It hasDDR2 2x1GB sticks of RAM. So I bought a 2GB DDR2 stick thinking I could get a total of 3GB. When I installed the RAM with the new 2GB stick and the other 1GB stick the screen went black. I tried the new ram by itself and it runs fine. What is the problem, why can't I run 2 slots like I was before? My GHz on the new RAM is 667GHz and the old ram is 533GHz (I think). I heard they should be fine and the package on the new RAM says its compatible with AVC/CON >667MHz >533MHz >400MHz. I don't know if that means it compatable with other memories. HELP ME.