Change your Windows Update settings!

WARNING! Change your Windows Update settings (to "Check for updates but let me choose whether to download and install them") right away if you don't want your Windows 7/8/8.1 updating to Windows 10 automatically!

http://www.forbes.com/sites/gordonkelly/2016/02/02/windows-10-automatic-installs-for-windows-7-windows-8/