lewin1 :
Thanks for the fast reply. But I am still not convinced. You said my product key will be superceded by windows 10. So I will still be getting a product key for windows 10.... right??
If I understand correctly from windows 8.1 onwards OEM is abandoned. That means I will be getting a windows 10 retail version. Why cant I use it for the new machine??
You understand wrong. OEM keys on new motherboards are written into the BIOS, they still exist and ARE OEM. When you upgrade to Windows 10
you do NOT get a new license, you only carry over activation!
In simple words, you cannot use your license on another machine. Even if you have a retail Windows 7 license you cannot install Windows 10 that was upgraded using that license on any other computer. You must first delete Windows 7 and 10 (upgraded from that license) from all computers before installing either on a new one.