I've seen it implied that if you upgrade your OS to Windows 10 (from 7 or 8.1) that the product key of your old OS (whatever you've upgraded from) becomes invalidated? I also understand that there is some kind of hardware authentication so that if you ever have to do a clean install of Windows 10, you can do so, but that it will be activated based on a "fingerprint" of the hardware stored by MS?
Are those points correct?
Now, something that concerns me, is if you had a Full Retail operating system (not OEM) prior to upgrading, you would have been able to move this from one system to another. As long as you only ever had it installed and in use on one PC at a time, you could transfer the OS. This is not just a theoretical benefit, it's something I've done many times, and why I would normally go for retail rather than OEM packs.
Does anyone know how this could work following upgrading? If the old OS's product key is invalidated, presumably it won't activate and therefore it would also not be possible to upgrade it to Windows 10. But if you want to transfer to new hardware, there will be no record of the system ever having been authenticated previously. At this point, will you be required to buy a new license??
Apologies if this has been covered, and thanks for any definitive info!