My dad has a problem with his pc which I have been trying to help him with. He was working on it one day and the screen just went blank. The PC eawas still running and the power light was still on on the monitor. All he could do was to turn off the power and reboot. Now, on re boot, the screen has the XP welcome screen, albeit through a haze of horizontal lines, then the screen is filled with what looks like space invaders gone wrong. The pc appears to be booting correctly with all the lights coming on for each drive. But you cannot see anything on the screen. I have swapped the monitor with mine and his monitor works fine on my pc. I have tried booting in safe mode but nothing is displayed on the monitor so I cannot see what it is doing. Any ideas what might be the problem and how I can eliminate each thing. I am thinking memory, graphics, video, and maybe a motherboard. The pc is 18months old, has XP 256mb ram and a celeron processor.