If you’ve upgraded from Windows 7 or 8.1 and your Fn keys are dead, this utility is your first and best solution. Keep a copy of the installer on a USB drive—future Windows updates have been known to overwrite it.
The utility is installed, but the background service required to launch it at boot has been disabled in your system configuration. Step-by-Step Guide to Download and Install toshiba function key utility windows 10 64 bit
Turn it on and repeatedly tap the key (or F12 on some models) to enter the BIOS setup. If you’ve upgraded from Windows 7 or 8
Visual confirmation bars when changing brightness or volume. toshiba function key utility windows 10 64 bit