We noticed that a lot of customer PC’s where coming in with the same problem after installing a Windows update, specifically the April update. After a few hours of troubleshooting, the only conclusion to fixing the problem was creating a USB Windows 10 installation media and reinitiating the update process from the USB media (It will reinstall windows but download everything via USB update instead of the OS). We tried everything (sfc /scannow, dism…) and this was the ONLY solution that worked. So the solution to your broken windows is simply restarting the updating process through a Windows 10 USB installation media, the process should leave all your old files intact and only fix the broken OS, specifically the Administrative/System accounts which is what caused this problem originally.