EIther that system has previously had Win 10 on it. Or it has a Windows 8 key in the bios and they downgraded it to 7 in the past.
Now this is becoming very intriguing!
I actually built the system from sourced parts several years ago for the client. Windows 7 was installed and has never been upgraded to my knowledge.
I had not seen or heard from the client for about 8 months prior to this so a family member or someone else may have upgraded it then rolled it back for him?
Maybe the thought was to upgrade to Windows ** to remove the viral/malware infection. Who knows.
The client would not be capable of doing such and upgrade himself.
I am puzzled as to why it did not ask for any key, but obviously there must have been an upgrade at some time that I am unaware of. The client never mentioned it, so I never asked.
Edit: Looking back at my records the computer was built in March 2013. There was an issue during the build where there was a problem with the Motherboard. (I didn't record what the problem was though). I sent it back for a replacement so maybe I got a used one in return?
That was before Windows 10 so maybe the replacement board was from a computer that had had Windows 8 installed.
Now that's opened another can of worms re license legality! Not to mention an uscrupulous supplier sending me a used? board!
He might be purchasing a retail copy of Windows 10!
Second edit: But back then it wouldn't have been an UEFI board???