The "NK _" is trying to boot a UEFI boot ROM in a BIOS boot mode.
The utility is only supported on UEFI. There is a DOS utility that you could use if you don't want to change your boot mode.
Change your BIOS setting from BIOS to UEFI for boot mode and the "NK" won't appear anymore.
The "NK" occurs when you boot a EUFI utility like Nautius in BIOS mode.
Change your boot mode in the BIOS configuration to EUFI and the "NK" will go away.
A DOS utility is also available if you don't want to change your mode.