After trying to revert to Windows 7, it wasn't fully recovered (the scheduled tasks, created by Windows, remained corrupted). So I had to restore Windows 7 from my backup. But it seems iTunes remain confused ("can't sync due to unknown error") as apparently some permissions in user directories remain different than initially even now?
So I've added some registry entries which were supposed to mean "I don't want Windows 10." And I've hidden the updates that install "Get Windows 10."
Yet not only the Update tries to install the "Get Windows 10" every month (un-hiding the updates without me!), the updates last for hours (the famous svchost looping in some unnecessary checking of something that doesn't have to be checked almost infinite number of times).
(Unfortunately Linux isn't working optimally on the notebook either, making the touchpad unusable and not handling the vendor Fn keys.)
Now I know that the nags came with the security patch of IE, which means that I can't even avoid it if I want to have security updates installed. Horrible. How is then that the nag doesn't happen for business users if it's a part of the security patch?