Returning to Windows 10

Although I see various Windows 10 installation posts, mine might be an unusual situation, so want to get advice before proceeding. My new computer is Windows 10. As the release works well I want to install windows 10 on my old computer.
That computer was bought as a Windows 10 computer when Windows 10 was released.It had a WIndows 10 sticker on it as well, however it actually had Windows 8.1 installed, and a button to click to upgrade the first time I used it. When I did so I received notification from Microsoft that I would be notified when to install it. When that happened a couple weeks later I completed the install, but the release had multiple problems, and I reinstalled from my drive. It returned the system to 8.1, which I was more than happy to use over the next several years.

I'm under the impression that I will need a product key to do a fresh download? I'm not sure if Microsoft issued a product key when I made the initial Windows 10 install, or if so reference to it might have been wiped out when I returned to Windows 8.1. What can you advise?

When you upgraded to Windows 10, a "digital license" should have been created. What this effectively means is that Microsoft stores a digital signature of your system on their activation servers and any time in the future, when you reinstall Windows, the process of activation will recognize that Windows 10 has already been activated on this system. As a result, no key is needed.

In other words, you should not need any license key when you reinstall Windows 10. Just make sure that you use the same edition of Windows that was previously installed (Windows 10 Home, Pro, etc.).

My suggestion would be to create an image backup of your current installation just to be on the safe side in case you need to get back to the current state if you have any difficulties.

Hi,
Shouldn't matter
I just used the media creation tool yesterday and used it on a win-7 laptop
No issues to speak of digital license was shown after so obviously ms doesn't really care.
I never entered a activation key.
I did how ever disconnect from the interest once win-10 blue screen was entered to show the final search for updates.
It's quicker anyway and I got to keep the local user account without being pestered into a ms one creation.