Upgrading new Win 10 system to PRO, moving Win 10 HOME licence

x509 said:

My wife is about to get a Lenovo laptop with Win 10 home. All other systems in our home network run Pro, so I'm thinking I should use an extra Win 7 Pro key to upgrade that laptop. Will that approach still work?

Yes, that should still work. It would need to be a retail W7 Pro key that is not in use on any other machine to comply with the EULA.

Also, I seem to recall reading somewhere that I should also "save off" the Win 10 Home license from the laptop so I can use it in the future. How would that work?

A machine supplied with W10 Home pre-installed will have an OEM W10 Home key embedded in its firmware. According to the EULA an OEM key is not transferable, being tied to the machine on which it was first installed. You can read the embedded key from the bios (and confirm its type) with ShowKey Plus.

ShowKeyPlus - Windows 10 Forums

x509 said:

Thanks. We don't have that new system yet, but I'm afraid that you are right. So I guess all I can do is install that Retail version of Win 10 Pro and "throw away" the OEM install of Win 10 Home.

Well, if you have a Win7 Pro key that's not in use on any other machine it should be able to upgrade the installed OEM Win10 Home to Pro.

Windows 7 product keys will not upgrade Windows 10 Home to Pro.