To allow USB keyboards to work before the OS is loaded. I'd check in there.
I am having a weird problem, my Keyboard won't work on the Post bootup however when windows starts it does work. If i want to go on BIOS or press F8 ect it won't work, also i get the message "Keyboard not detected". I have a USB keyboard, i reset the bios to default to make sure my usb ports were enabled.