I upgraded from Windows 7 home to Windows 10. Later, while cleaning out my IT room I found an unused copy of Windows 7 Ultimate sealed in the box. I know that if I upgrade to Windows 10 from Windows 7 Ultimate, I get Windows 10 Pro rather than Windows 10 Home.
So... I went to Settings/Update & Security/Activation and changed the product key. The Windows 7 Ultimate key was refused.
Which leads me to my question, "How do I upgrade to Windows 10 Pro from Windows 10 Home using a Windows 7 Ultimate product key _without_ reformatting the hard drive and doing a fresh install of Windows 7 Ultimate"?