If you do a clean install with the Media Creation Tool, it defaults to Windows 10 Home instead of offering Pro, even with a valid Pro or Enterprise key.
If your computer originally came pre-installed with consumer editions of Windows 7 Home Basic/Premium or Windows 8/8.1 Core or Single Language, you might want to perform a clean install to Windows 10 Pro or Enterprise. Unfortunately, the installer created from the Media Creation Tool will default to Windows 10 Home instead of offering the choice of either Home or Pro, even if you use a valid Pro or Enterprise key.
On systems that came preinstalled with Windows 8, Microsoft introduced a new mechanism for product activation. Instead of using the old OEM SLP (System Lock Protection) key method, which allowed major brands such as Dell, HP, and Lenovo to install Windows in bulk, a unique product key is embedded in the firmware of the computer. This also removed the need of the Certificate of Authenticity stickers you would see attached to a PC running Windows 7 or earlier versions. Microsoft describes the behavior as by design, but it’s an extra bit of chore and confusion when setup is complete. Here is how you can work around the issue.
Upgrade to Windows 10 Pro Using a Premium Business Edition Windows Key
The Windows 10 November Update introduces the ability to use your Windows 7 or Windows 8 product key to activate the operating system. The problem is if you have Windows 10 Home installed, a Windows 7 Professional, Ultimate or Windows 8 Pro product key will not be recognized as a valid even with the Easy Upgrade wizard.
What you will have to do instead is use the default Windows 10 Pro product key to upgrade to Windows 10 Pro. Enter the following key: VK7JG-NPHTM-C97JM-9MPGT-3V66T.
Note: Don’t worry, this a publicly known key used for diagnostic purposes. No, it will not activate Windows 10 Pro installations for free.
Wait while the upgrade takes place. Your computer will restart a couple of times.
After that, you can then use your valid Windows 7 Professional/Ultimate or Windows 8 Pro product key to activate Windows 10 Pro.
You should now have Windows 10 Pro up and running successfully.
This process a bit convoluted, but it does work out in the end. Hopefully, Microsoft releases a fix to this in 2016.