New
#11
Correct. Booting from media is a clean install. But if the user starts Setup from within Windows he is not asked for a product key so all that happens is that he upgrades his Home to Home. He never has the opportunity to tell Setup what he really wants to do. With the clean install he does have that opportunity and the product key is the tool. That gives him his migration from Home to Pro without having to purchase the Pro Upgrade from the Microsoft Store. His computer becomes activated by digital entitlement for both Home and Pro. Should work that way. The last version of Windows that used that method to select which edition to install was Vista.
Then you will have buy the Pro Upgrade. There is no way to simply enter a product key to do it. Microsoft is not going to let a user with Home turn it into Pro without a purchase or already owning a Pro license. Since you own the right to a Pro license (7) I see no need to buy another one (10). I would save the money and back up your files and after installation reinstall your programs and restore your files.
Because the Windows 10 Home product key is not a retail key. It is the dummy "giveaway" key that everybody with the free Windows 10 upgrade has. It is blocked on Microsoft's activation servers just like OEM keys. If there were a way to enter a product key during the free upgrade you could do it that way, but there isn't. Contact the Store. When you buy online the digital entitlement is zapped to your computer. There will be no Pro product key sent you in an email. All you get is the download link in an email (I think).
As an aside: My wife installed Pro and then went online and bought Pro ($200) because she thought that was the way it worked. All she got was the digital entitlement for the already installed Pro. No download link. Microsoft sensed it was already istalled. (She didn't know about the Pro Upgrade (sigh).)
What you need to do is back up your files and restart with the Windows 10 media and reformat the hard drive. Then after you select Pro and installation proceeds put in the 7 Ultimate product key when asked. Or if you don't see a place to select an edition, putting in the product key when asked will make that selection. By the way, Pro is the default installation if no selections are made.
In other words you need digital Entitlement from Windows 7 Ultimate to get Windows 10 Prootherwise you can get digital entitlement via a clean installation of 10586 and entering the ultimate key during setup
You can clean install Windows 10 Pro (10589) and enter your Ultimate Product Key - to get a digital Entitlement activation
It does not appear that digital Entitlement is an upgrade path from home to pro