It's a button!
You press it! Lots of computers ONLY have a power button nowadays. How hard can it be?
Sometimes it's labelled.
I'll admit, the standard 1 / 0 label is a little obtuse (lots of my students aren't aware of the standard layout or symbols for tape recorder and VCR buttons, either), but if there's just a couple of switches on the front of the noisy box under your desk, you'd think someone would take the initiative to, oh, I don't know, press them, maybe?
Turning it off might be a different matter, but if these helmet-wearing rejects from the short bus can't manange to remove their fingers from their collective noses long enough to find "on/off" there's no hope for humanity.
I'd fully expect a central African Hutu tribesman - someone with no cultural context in which to place the noisy beige bringer of pornography - to figure out how to turn a computer after a moment's investigation.
Turning it off? I can sympathize with that one. Not being able to use a mouse or a keyboard? OK. I can accept that. But not that there are people too stupid to find the little bull's-eye that says "Press Here".