If you turned off your computer before a Windows update finished installing, you will very likely have an unfinished update applied which destabilized your system. Try to see if you can boot into SAFE mode. When you first turn on the computer, press F8 like once ever second until you get the alternate boot up menu. From there, select to boot into safe mode with networking. This may restore your core essential files so that you can start up again normally the next time you reboot. If not, we can troubleshoot from there.