Thanks for the suggestion. Unfortunately, I did originally boot with one stick only and then installed the OS. I then installed the other 3 sticks. All went fine. Then I manually adjusted the ram speed to the ram spec and I have not been able to reboot since. I've tried each individual stick without the others and still no boot. I could have set something wrong in the bios but have tried removing the battery etc and resetting but still no boot. The only way I can even get any beeps is if I start the system with no ram in it when I get one long beep followed by two short ones. As soon as I put in one stick it's dead in the water. What's confusing me is that it booted first with one fine and then once with all four. Now I can't even get into the bios. I've tried so many combinations my fingers are sore!