Windows sometimes has access to BIOS brightness settings under power management see if you can access the brightness there. If you cannot adjust brightness you may have ran into a snafu with your BIOS upgrade. Things you need to remember is if the function worked before the BIOS update? If yes then you can actually RELOAD the same BIOS and hope the setting is restored. If no then there could be hardware failure somewhere in the system maybe something as simple as keyboard malfunction. Ensure that the fn key works by using other fn functions.