OK, Ed Bott of ZDNet has posted a couple of reg files, DisableOSUpgrade.reg and DisableGWX.reg. Download them, double-click them, and they will change the registry for you.

See: How to block Windows 10 upgrades on your business network (and at home, too) http://www.zdnet.com/article/how-to-block-windows-10-upgrade...

The two small text files are at https://onedrive.live.com/?authkey=!APe8Z7RJNVNc0uM&id=FEA7E...