So, let me ask why. I know some of the benefits to having a stand alone ISO, but for most users it is unnecessary. What is your thoughts on this being a "must do" process? The ISO install still needs to be registered or "certified" against a qualifying Windows 7 / 8.1 build.
Based on an assumption that several things are true:
- you have a machine that's not yet been upgraded
- you are worried how long you might have to wait for the automatic upgrade to happen
- you have the 10240 ESD file on another machine (same edition and bits)
Since the downloads for Windows 10 ISOs aren't officially available anymore, you can't upgrade it in the normal way by installing a previous build and running Windows Update. You can't upgrade directly from 7 or 8.1 through Windows Update without waiting an unknown amount of time until "your" reservation is ready.
The process of turning that ESD into an ISO is much less convoluted than figuring out how to copy it over and make windows update see it on another machine, but that too is possible. (footnote)
In my experience so far, a Windows 7 or 8.1 machine that has never had any Microsoft Account tied to it, and never been in the preview program, upgraded and activated to Windows 10 just fine by mounting the ISO and running setup.
As far as "must do" - in my situation at work, it is prohibitive to have a large number (more than zero) machines download a 3GB ESD over Windows Update because of our slow Internet connection. I've been able to upgrade a machine at home, grab the ESD from the hidden $windows.~bt or whatever that folder is called, make an ISO from it and carry that to work the next morning.
Footnote:
Finding the leaked WZOR builds is even easier but I didn't say that