What version of Windows do you use? My desktop uses the latest version of 10 (AFAIK) and the shut down button reads something like "Shut Down and Install Updates" when Windows wants to install an update. I also remember 7 having a little orange icon next to the shut down button when it was going to install an update.

Granted, I don't think there's a way to properly shut down without the update in an I-have-five-minutes scenario. But it does, at least, warn you.