In case you missed it, support for Windows 7 is coming to an end on January 14, 2020.
Microsoft allows users to use the Windows 7 key to activate Windows 10 because the PC has a ‘Digital License’ (key) to use Windows XX.
Win 7 version must match Win 10 version, meaning Windows 7 Pro key to upgrade to Windows 10 pro or Win 7 Home key to upgrade to Win 10 Home.
I could be wrong here, but I think the key (digital license) for Windows is married to the PC, so you can’t use a Win 7 key from one PC to put Win 10 on a different PC.
Here is a walkthrough of how to do it:
https://www.tenforums.com/tutorials/139745-upgrade-windows-10-windows-7-free.html
Windows 10 version is currently 1909 so the website above is up to date.
The user has the option to do an upgrade or a clean install.
