Sync. Out of Range

When I turn on my PC(HP Compaq DX2000), my monitor displays a “sync. out of range” error. Nothing else is displayed except this error message. I’ve tried using different types of monitors but I still keep on getting the same errors. I can’t even go into the PC BIOS or Safe Mode because it does not show anything at all except the error. I’ve tried using another VGA card but the screen remains blank and shows the same error.