How to undo a system upgrade

I really goofed tonight. Before I left for the road, I took with me (what I thought) was a Windows 10 ISO, and I wrote down the product key on the DVD I burned it to, which was months ago. I did so, thinking that I would eventually "try" the Win 10 on the laptop. Tonight I got bored and pulled out the DVD and began to commence on the install. Outside of being bored, I was/am extremely tired. What I actually put in there, was a Windows 7 Professional ISO! My silly brain cells saw the screen that said (Upgrade or Full install), and of course I was thinking oh yeah, I am upgrading to 10. So I chose upgrade and went back to my coffee (which wasn't strong enough obviously).

So overall, I upgraded to exactly what I was already running! Then once Windows loaded, I saw that my wonderful product key was not working. I got on a chat with a Microsoft guy, and asked him to look up my product key. He came back and told me that it was in fact a Win 10 pro key, and a retail version at that. He said it was locked, and just needed to be released. He and I both were amazed that I had a retail key. Where I got it, couldn't even come close to telling you.

So now what I have is an OEM Windows 7 Pro installed and running, and it is begging for a product key in order to activate. I have searched google like crazy in looking just for a key, but am quite hesitant in doing so, because some nut from some third world country is probably sitting there selling keys he dreamed up.

If I were to call Microsoft on Monday, you think they would be able to tell that I actually had an authentic version of Win 7 Pro before I made this goof, and just issue me a product key? They no longer sell retail versions, and I can't even upgrade to 10 until I have an activated OS on this laptop. I feel screwed literally.

Any help would be greatly appreciated! Thanks

Your specs show Custom build.
Did you build the PC yourself, or order a custom build from someone else ?
Do you have the original install media and product key used ?

Do you have a System Image Backup from before you did the upgrade ?

Do you have a Windows.old folder ?

Hi David, you are looking at my (home) PC specs. I am on the road with my laptop, which is an ancient (Sager NP 9262) that has a Clevo board. The original install media for Windows 7 Pro 64B is about 400 miles away now. Unfortunately I do not have a system image backup either. I have searched for the Windows.old via windows explorer, none exist.

What I did, back in Aug or Sept of last year, was I (thought) I downloaded and burned to this DVD I have now with me, the ISO for Windows 10 Pro 64B. Then I wrote the product key on the DVD. Apparently whatever site I got this from screwed up their links, as this DVD has Windows 7 Pro 64B, and not Win 10. The product key I wrote down is in fact a "retail" version product key for Win10 pro 64 bit, according to a MSFT chat tech, but it is locked, never used before, and just needs to be released. So again, yesterday, I proceeded to install what I thought was Win10. Once at the (upgrade or full install) screen, my tired eyes went ahead and clicked on upgrade, which meant keeping my programs and files. In essence, all I was doing was installing the exact same OS over the other, except this is an ISO "OEM" file of Win 7 Pro 64B of a DVD, and not a CD from the original retail packaging.

The laptop product key label located underneath is for Windows Ultimate Vista, which obviously is of no help to me. So all I know at this point, is to call MSFT on Monday to see if they can clear this up for me, and if not, then I will have to wait until my return home, which is two weeks away. I should have never purchased this $5K laptop in 2009, as today, the company is out of business, and if you need to replace a battery, etc., forget it, no longer in production. Even drivers for the Motherboard, or BIOS, have never been updated by the manufacturer since roughly 2010-2011.

I am just trying to learn if there is any sort of workaround on getting this installed version of Win 7 pro 64B activated with a product key, of which, I do not have. Or option two, some means of digging into directories or otherwise, to possibly find a way to revert back to the old and most recent OS, that I had before I made this goof last night. Thanks for looking into this..

Hi Colarguns,
Have a read of this tutorial, but as you already have a key ignore steps 4,5,6.
Windows 10 - Clean Install - Windows 10 Forums

Roy