From: https://support.microsoft.com/en-us/help/3080351/how-to-manage-windows-10-notification-and-upgrade-options

To block the upgrade by using Computer Configuration, follow these steps:

Click Computer Configuration.
Click Policies.
Click Administrative Templates.
Click Windows Components.
Click Windows Update.
Double-click Turn off the upgrade to the latest version of Windows through Windows Update.
Click Enable.
Policy path: Computer Configuration / Administrative Templates / Windows Components / Windows Update Policy
Setting: Turn off the upgrade to the latest version of Windows through Windows Update

From: http://www.windowscentral.com/errors-windows-10-upgrade-fix

Fixing message 80240020 ….

Also: http://www.digitaltrends.com/computing/common-problems-with-installing-windows-10-and-how-to-fix-them/

Also: http://windows.microsoft.com/en-us/windows-10/upgrade-install-errors-windows-10

Also: https://www.microsoft.com/en-us/software-download/windows10

Manual Download

Also: http://www.infoworld.com/article/2989972/microsoft-windows/windows-10-installation-problems-and-what-to-do-about-them.html

From: http://download.wsusoffline.net/

Using "WSUS Offline Update", you can update any computer running Microsoft Windows and 
Office safely, quickly and without an Internet connection.

From: http://www.infoworld.com/article/3105605/microsoft-windows/2-easy-steps-to-speed-up-windows-7-update-scans.html

Also: http://wu.krelay.de/en/

Make sure you have KB 3078601, 3109094, 3138612, 3145739, and 3164033 installed
Find this month’s favored patch and install it