Hi, I have a Compaq Presario Desktop PC running Vista. Up till yesterday it's been fine until the computer froze on the screensaver and did not respond to anything even CTRL/ALT/DEL and had to do a cold reboot. On startup had the usual message about computer not shutting down properly but did startup ok. It did this about 4 times but now when you switch it on it does nothing, the fans start, hard drive spins up and thats it, cannot get into bios & nothing on screen. Any ideas ???