George's Windows machine force upgraded to Windows 10. Microsoft says that upgrading to Windows 10 is "normal behavior" when Automatic Updates are turned on. That will update critical updates by default. There's also 'Recommended Updates' which is also set to automatic by default. Windows 10 was set to be a recommended update, which is why it happened on George's PC.
The End User License Agreement actually pops up after the install and if the user says no, it actually uninstalls it to the previous version. If George did accept it, he still has 30 days to roll back. George should go into the the recovery options and there will be a rollback option. It doesn't always work, though, and could cause his system to be rendered unusable. He'd have to run the recovery option again from a backup recovery key or CD, but that won't work if he didn't make one.
Once George has rolled back to the previous version of Windows, he should get Never10 so it doesn't upgrade him again.