was messing about in the bios the other day and tried to be clever and think i done something to the overclocking part only slightly. but when it restarted it poered up but there was no beep and nothing on the screen, reset the cmos but just the same.
If you can't get into the bios try taking out the motherboard battery and move the jumper to the bios reset pins. Move jumper back afterwards and replace battery. This should have reset bios to original default settings and undo any changes that you made. Then try restating system.