Upgraded to Windows 10 from Windows 7 Ultimate, it worked but it went badly (installed on the wrong hard drive), so I restored backup, deleted an old Windows 7 config from the boot manager in msconfig, and deleted the old installation of Windows that it pointed to.
I then tried to upgrade again booting from a USB I created with the Media Creation Tool, and now it won't accept my Windows 7 Ultimate Key.
I understand that when the free version of Windows 10 installs, it gives you a key but doesn't tell you about it. Since I restored my backup, have I lost my key? Or is there a way to get it back?