Restarting or shutting down in the middle of a Windows update installation may cause serious damage to your PC. It all depends what the update is and where it was in the installation process when you shut down.
There are several things that could happen when you shut down before the Window installation process is complete. You could get lucky, and, when you power back up, your computer could just resume the installation process. You could corrupt only non-vital files which would only require you to “restore Windows to an earlier state.” Worse yet, your system could become non-bootable and require a Windows Recovery CD to check and repair errors or a complete re-install of Windows.
You can try the following: First reboot and wait for it to get stuck. Then long press the power button for a hard reset three or four times. This should get you to the troubleshooting window which should give you options from which to choose, including refreshing or restoring Windows. The easiest option, however, may be to pay a visit to Computer “A” Services. Our experts are veterans at computer repair and well-versed in all of the latest and greatest solutions.
Additionally, if your computer freezes during a Windows update install, it could be the sign of a very serious problem, and you could experience file damage and poor computer performance due to a partial update, your system could become unbootable and get stuck in an infinite loop or you could suffer from total data loss. This is also a case for Computer “A” Services.