you may be in a restricted environment with no boot option selections, like on some VPS and dedi server providers.

i've seen similar techniques used to shove windows on "linux" VPS/dedis boxes by booting into rescue mode and then applying a raw Windows boot image that's preconfigured and rebooting back to the Windows install and hoping you stood the image up right.

good ol' days of getting Windows up on Kimsufi boxen.