Cfoyster, Maybe your mobo slots 3,4 are faulty. If I were you, I would try single ram stick on all slots. I would place my ram on slot 1 and 3 if I had two.The screen, mouse and keyboard work fine if I put the ram in slots 1 and 2 but not if I put the ram in either 3 or 4. The motherboard is a us prime z270 is this a fault with motherboard do you reckon?