From Dj's post that I lost . From the winsupersite http://winsupersite.com/windows-10/windows-10-clean-install-using-media-creation-tool#slide-0-field_images-57241
The other way to clean install from a valid Windows 7 or 8.1 system is to use the same media creation tool but instead of creating a USB drive to boot from just select the option to Upgrade this PC now. That will download the Windows 10 ISO and begin the upgrade directly in the current OS.
I then selected to keep nothing from the Windows 7 OS in this case so that meant no settings, files or anything was transferred into the new Windows 10 installation. I was also prompted to go through the entire Out Of Box Experience (OOBE) by selecting my basic settings including logging in with my Microsoft Account.
When I logged into the desktop it was a clean installation of Windows 10 with only my info provided during OOBE there.
This was such a clean install that the Recovery option that is normally available for 30 days after upgrading Windows 7 or 8.1 was not even present.
I then checked the system page and it showed Windows 10 was activated and ready to go.
There is no reason to believe this same process would not work with a properly activated Windows 8.1 system as well.
See the screenshot gallery for a walkthrough of the entire process.
Let us know how your own upgrade situations go in the comments below.
I added the winsupersite link