My PC won't boot... no display ...but power led on motherboard is lighting ....PSU working .....cpu and gpu fan running the DVD drive works....but it just won't display or boot. What do I do ? please help. I tried running my mobo with a different PSU but the same thing happens. Also to mention my system simply starts without even touching the power button. I tried mobo CMOS reset ..no good . A different GPU ....no good. The mouse and keyboard power up fine though.