Use the F8 key during boot to access alternative startup options. Instead of choosing Safe Mode, there is an option to Disable Driver
Signature Enforcement. Select this and see if you can get into Windows. I am working on a computer that is giving that error during a failed System Recovery. The user managed to create user accounts somehow but then it got stuck on installing a software package (22/23). When I used the DDSE option I got to the initial screen to choose a user account. When I logged in, it resumed the software installation where it had gotten stuck before. That installer hides the fact that Windows is running behind it. If you use Ctrl+Alt+Del and start the task manager, the installer hides it too. However, if you use Alt+Tab fast program switching, you can bring the Task Manager to the foreground briefly but the installer will hide it quickly. Move your mouse cursor to the area where Task Manager appears because you can click once before the installer hides it again. Click once to highlight the task that's running, then again on End Task to get all the way into Windows.
The customer in my case did not have any data to preserve so I just used Alt+F10 right after POST to begin a System Recovery.
Hope This Helps