Some other options to try, if you haven't already and assuming you are running Windows 10,
- startup to the Windows 10 logon screen, in the bottom right-hand corner of the screen you will see a 'wheel/power-off' type icon, far bottom right-hand corner, which if you click it will display 3 options, one being 'Restart'.
If you hold down the keyboard 'Shift' key and click 'restart', then keep holding down the pressed 'shift' key whilst windows restarts, Windows will reboot into a 'Choose Option' screen. One of those options displayed is 'Troubleshoot'.
Click 'Troubleshoot' and you can then try either 'System Restore' option to revert back to a previous Windows 10 restore point, or the other to try is attempt 'Start-Up' repair.
A third option, assuming it can find the necessary files intact, is to select 'Reset this PC' from the 'Troubleshoot' Screen. With that option it should give you the opportunity to return to your previous Windows Version, as long as it is not 30 days passed since you upgraded to Win 10.
Hope that helps.