My Toshiba P755 hard drive failed shortly after win 10 upgrade from windows 7. Reformatted as NTSF and now have win 10 setup on bootable usb flashdisk but cannot get to the P755 bios to change to boot from the usb. Tried FN F2 with no success, Any other key combo gives 10 system characters on screen. Need help to get to bios to change boot to usb.