I had 2x4 DDR3 - 1600 Hyper X RAM before. I decided to add 2x4 to that so that I could have a total of 16GB of RAM (same type of RAM), but my computer would turn on (fans would operate) without getting to the BIOS. I would remove the 2x4 I added and my computer would work fine. I have since then took out all RAM and now no matter what combination of sticks I use (even the original), the computer will turn on (fans) but not even get to the bios (no visual).