This problem has been elevated to a whole new level. MS has just announced that if you turn on Automatic Updates in Windows 7 or 8, you WILL find the Windows 10 installation process started on those machines. At that point, if you’re paying attention, you can turn it off. Most people will just click through the dialogs and accept the installation, like they do with everything else.

I’ve never allowed automatic updates to be turned on for any Windows computer I’ve ever owned or administered. I suggest that other people adopt that policy, and quickly.

(Just one of many sources for this: http://www.forbes.com/sites/gordonkelly/2015/10/30/windows-10-upgrades-now-automatic/)