I used the $39.95 downloadable version, and installed it to a
blank disk. Next, ran the "Refresh your PC" function, which
partially reinstalls the system. (There's a recipe for this,
so I didn't think it up. It's along the lines of the
"double install method" used previously.) The system was activated
after that. So no pre-existing OS was used during the install.
I've had upgrade versions of Windows before, where the installer
asked you to insert the previous OS installer CD. And this install,
didn't even try that. It just installed. After the first install
(with license key typed in), it did not activate. But after
the system refresh, and as many reboots as it felt it needed,
after that I checked the system control panel, and it was
activated. (I also tried the slmgr recipe, but that didn't work.
I had to spend the extra time on the refresh thing.)
(.bat file didn't work, but refresh did)
http://www.eightforums.com/tutorials/13375-clean-install-windows-8-upgrade.html
Paul