Would he have MBR these days? If it is GPT and UEFI couldn't he recover via the firmware? I had a Linux install trash my GRUB but I was able to recover by getting the firmware to boot directly into one of the working Linux installs on the machine. From that Linux I could then fix GRUB and I had a working machine again (though the faulty Linux install was still toast). Not sure if this can happen in the Windows world.
