Hi, I am working on a computer for my sister, but I am using only school parts, as my school believed it did not work, but when I used it it worked fine. Anyway, my parents current PC is running windows 10 but has a windows 7 product key on the side of it. Their PC is still in use, so if I copy that product key off that PC, and use it to activate the school computer, which I just loaded up with windows 10, would it work.
OEM keys will not be transferable as windows will do a bios check to see if the machine series matches the key. Purchased keys however are still yours and you own it. When you upgraded one pc to windows 10 you were given an all new digital key based on your ownership of a legit windows 7 key. You are still free to install that windows 7 key elsewhere. You could net several windows 10 upgrades this way but then again, there was very low security checking in the whole windows 10 process.