Someone said you tell them to turn it off and unplug it, because you need a number from the plug side going into the computer. Then you coach them through the process to find the right plug, and they don't feel stupid because this is a strange process.
Then when they say there's no numbers on the plug, you pretend like this is new and useful information, tell them to hold the power button and make sure no lights come on, and then you tell them to plug it in and turn it back on
Now, not only have you confirmed they definitely turned off the computer without asking a bunch of potentially insulting questions, the showmanship makes them feel like this is arcane knowledge you've taught them