Your Binary In/Out System is the first set of bits and bytes that build your matrix inside your PC while booting.
I don't know what Shadowed means but whatever you want to do to a good working BIOS don't do it. The BIOS is a set of instructions flashed into a memory-chip, it will never change without you doing something to it.
remember: If a PC boots without a harddisk and it will use a floppy or CD for setting up then leave it the way it is.
yes, i am also curieus about the answer.