I agree with Regedit32.
I would even include "everyone", that is "everyone" should have in their possession a full version of the Windows 10 installation media that matches their current install.
Unfortunately, because of the way that Windows 10 is delivered, many people do not take the additional steps to obtain such media
https://www.microsoft.com/en-us/software-download/windows10
Using that link to download the ISO. The tool will also help you create the media you need or you could use something like
Rufus
http://rufus.akeo.ie/ to create a bootable USB ThumbDrive
OR
ImgBurn
http://imgburn.com/index.php?act=download to create a bootable DVD
Either of which can be used to boot the PC and then using the Repair your PC link to get to the troubleshooting advanced options to further diagnose the problem and hopefully resolve some issues.
It's by no means a magic bullet but without it you might be left just staring at a blank screen.
With it you at least may have some options to investigate