After firmware version 1.65, Areca RAID card ARCxxxx.BIN code creates a virtual bootable disk (UEFI OS) for RAID controller ARCxxxxUEFI.BIN code to launch the McBIOS setup utility. When M/B setup chooses to boot from the virtual disk, the McBIOS setup utility is launched through boot into UEFI OS during M/B boot. This motherboard bios may add the new boot device (the new firmware feature: UEFI OS) as the first boot device. Please enter the setup of M/B BIOS to disable or adjust UEFI OS in the boot option priorities if it is the first priority of overall boot order. Otherwise the system will always boot into UEFI OS without using the hotkey.