DZ77-GA-720K halts at the BIOS prompt and won't proceed on reboot. If power is fully removed and system turns on, boot normally. Anyone have ideas what's going on?
Make sure there are no devices connected to the USB ports. Just keep the mouse and keyboard.
You also should consider updating the BIOS on the system. Here you can get it:
Try clearing the CMOS. Here you have the instructions: