I've had no formal training, but I handle as much of the church office IT as I can to try to save them some money.
A couple of years ago I upgraded all of the office computers to Win7, and after most of the dust had settled I upgraded them all to Win10. They have all been working fine for at least a year.
A few months ago the church hired a new staff person, so I changed the name of one of the computers from "User-PC" to the Function this person would be handling. It is a Compaq that came with Vista installed.
I now get text in the lower left hand corner of that system saying I need to Activate Windows 10 Pro. Before I changed the computer name, I used Keyfinder to get the Win10 Pro key, but it isn't accepted when I enter it.
At least two of the Win7 updates were done with a multiple use code as according to Keyfinder one of the other office systems has the same Win10 Pro code.