Running an ASUS M2N nForce board...decided to upgrade my from 2 GB of RAM to 4 GB. I was previously using 2 x 1GB DDR2 6400 Corsair memory to 2 x 2GB of 8500 Corsair memory. Now, for some reason, when I pair both sticks together (in either channel configuration it seems) Vista will not boot. But, if I remove one stick, the system will boot. I checked both sticks for consistancy and they are okay. The ratings on this motherboard is DDR2 800 up to 8GB, so I don't understand what could be causing this problem?