Hello. I have a Dell Optiplex 755 SFF system that came with Windows XP and I've been having some issues related to its BIOS. Recently, I lost the option to boot to a USB device when hitting F12 repeatedly. I've done this countless times to install Linux distros from a USB flash drive, but now the option is missing. When I went to check the boot sequence, the BIOS refused to give me access to change it. There's not even a boot option for USB listed in the boot sequence. All of the USB controllers are enabled and I've already tried resetting the BIOS to its defaults. I even messed with the jumper on the motherboard and flashed an older revision of the BIOS, but I haven't got any luck. I did boot to a recovery disk through an external DVD drive before this happened, but I'm not sure if this had an effect on the BIOS. Will I have to get a new motherboard or is there a way to fully reset the BIOS?