There are tools to stop it but my advice is to move to w10.
The ONE THING I am encountering is the W10 offer that folk click on the top right X and that looks to be coded as the Yes button instead of the cancel. This is the only repeatable action that I can duplicate here and get close to "W10 installed without my permission."
The OTHER THING is that W10 may download but not install which causes some folk to freak out.
My advice is to move to W10. I will do this on all machines at office and home before the 29th to avoid the costs of doing it next month.
Hi. I have a HP Envy laptop running Windows 8.1. I am afraid to allow any updates since I have heard of Microsoft hiding the Windows 10 upgrade in innocent looking updates. Is kb2919335, from 2014, for Win 8.1 safe to install on my laptop? I've read that it's an important update. It takes too much time to read the information about every update that is Important or Recommended. To keep from installing Win 10 unknowingly, what are the updates that we should not download and install? Thanks for your help!

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic