I have an ASUS P9X79Pro motherboard, and this is an issue which has annoyed me since a long time. I am running the very latest release BIOS, 48-something. If I need to boot off a USB or optical disk, I have to go into the Boot menu and select that drive in the Override section of that page. What I can't do is permanently set the boot order so that the Windows Boot manager is always third in the priority list, after USB and optical even when the optical drive is empty or there is no bootable USB plugged into the system. So what am I doing wrong?