Since there's no OS on the computer, the only things I can think of are:

• Use another computer and connect it to the JTAG header on your motherboard (assuming it has one) and write a script to drive your JTAG software to make the update.
• Write your edit program into an EPROM and boot the motherboard from the EPROM. (You used to be able to put an EPROM in many network cards for booting from the network. I don't know if it's still common or possible, though.)
• If you can set the values from the setup screen, get/make a keyboard faking device that you can drive via another computer.

...roboticus