I use GWX Control Panel to prevent the update of Windows 7 to Windows 10. Works very well.
Security updates of Windows 7 can still be installed. I have 2 PC's on which I had to return from W10 to W7: one for screen problems (screen too small and no native resolution) a second for a blue screen that I couldn't resolve. By the way I don't like the ugly W10 desktop and I installed Classic Shell.