How to upgrade to Windows 10 running from an ISO installation disk image

By Ed Bott for The Ed Bott Report

....I know long-time Windows users have wake-up-in-a-cold-sweat nightmares about Windows upgrades gone horribly wrong. But those days are long gone. I have done hundreds of clean installs and upgrades, on physical and virtual machines, using the Windows 8.1/10 installer family.

The staged installer used with Windows 8.1 and Windows 10 is as close to failsafe as software gets. If something goes wrong, you can roll back easily. (I've done those rollbacks a lot during this beta.)

After the upgrade is complete, you can create an ISO file from the cached upgrade files.

Or you can start the upgrade, wait until the installer files are fully downloaded, and then cancel. In either case, you'll find the large installer file stashed in a hidden folder called C:\$Windows.~BT, in a subfolder called Sources.

Here's how to find it in File Explorer. (Note that I've enabled the option to view hidden files.)

Read full article here:

http://www.zdnet.com/article/how-to-turn-your-windows-10-upgrade-into-an-iso/