lx07 said:
Not necessarily. You could run it from Preinstallation Evironment (you can download a version of PE with ShowKey already installed from here - Windows 10 Recovery Tools - Bootable Rescue Disk - Windows 10 Forums). PE runs from RAM and doesn't require any OS to be loaded.

Whether that is more efficient than guessing (if you haven't already downloaded it) is open to question though as installing Windows doesn't take so long anyway..

Anyway it is a useful tool - if you have a spare USB key you could consider putting it on it in case of future problems...
Another Great Choice!!!! Good info lx07 :)