As the title reads I'm not able to boot to flash drive on my Acer laptop. I have Hirens boot program installed uising Grub4dos to configure the downloaded ISO of the hirens boot disk. when computer start press I F2 to enter the bios, I go to Boot and chose USB HDD then press F5 to get it to the top to number 1. then go to EXIT and press exit Saving changes. When restarting the computer it goes directly to the screen taking me to Windows 8.1. When going back to the boot options it shows that none of the changed configuration has changed. Any ideas?