The way i've always done it is via floppy drive.
I download and unzip the new bios to a floppy, restart the computer & when it reaches POST, press Alt+F2 to initialize the Bios Flash program.
It then reads the new bios from the floppy and flashes it on its own. You don't have to type or configure anything.
Oh, set your CPU & Ram to default speeds before you flash to avoid any mishaps.
Upon reflashing succesfully, I do a full boot up into windows, shut down and restart before making any changes again to the bios.