You're already answered yourself on this but just to share an interesting factoid... Windows 10 appears to be 'free' or at least nagware. In that you can install it on a new PC and although it will gripe about activation and leave up a watermark on the screen, it doesn't seem to deactivate at all. So should you ever need to, if you can add a suitably sized hard drive and install Windows 10 (to not muss up any original files) and preferably with the other hard drives UNPLUGGED until done with the install (so the Windows 10 install doesn't try to take over the boot process) you can use it to access original files and such sort of like a recovery partition.
I just had to do this and the win 10 install is still alive 3 months later still nagging about install. Other people report it seems to work just fine for much longer, none of the 30 day or 45 day stuff used to have.
You can also attempt to upgrade in place and it might fix Windows 7, it might not (but it will permanently upgrade you to 10 whether you want it or not, and if it fails in the process... i'm not quite sure what you do, since even a backup of Windows 7... well i'm not sure what happens to the original activation of it/whether it rechecks online servers and would claim you upgraded to 10 and can't rollback now)