I tried to upgrade Windows 10 from Windows 8.1 for a week before finding this thread.
Thanks to the advice here...after the installation files downloaded, when the "Creating Windows 10 Media" screen popped up, I unplugged the internet cord.
After primary installation, a screen popped up that said working on updates. Then I plugged my internet back in to let these updates download.
Yay! It worked. :-)