On 05/13/15, Microsoft published routine Windows7 Updates, which caused many of our workstations to become stuck on the "Preparing to Configure Windows" screen containing the warning "Do not turn off your computer". After waiting an ample amount of time for the updates to install in the background (e.g. 30 minutes), we pressed Ctrl + Alt + Delete and our Windows Log on screen re-appeared. The Windows Update Log also showed that all updates were successfully installed.