Windows 10: How to get back to my original license key's OS?

How to get back to my original windows license key's OS? I by mistakenly used a non-genuine microsoft key & now, it's not activating. I also tried using the powershell command "wmic path SoftwareLicensingService get OA3xOriginalProductKey". But the key it shows is saying that it's not valid.

:)

 

Need help finding OS license key

you can do a couple things.. Hope this helps..

• call your OEM and give them your serial number and they will give you the key.
• Install the new Windows 8 Developer Preview

 

Find Activation Key After Hardware Upgrades

The original 8.1 Pro licenses were all purchased, not OEM installed. I have all of the original cards with the License Keys, but I don't know which one needs to be used on this particular machine. What the steps in the earlier messages were trying to do was to find out which particular 8.1 license keys were used on my other Activated systems.

 

License Key Check

The only way to tell is to install and see if you can activate with them.

There are MSDN Windows 7 Retail licenses but they are not to be sold and they do get picked up by Microsoft.

There is no list kept of product keys.

I advise anyone wanting to buy 7:

Warning:

You do not buy a Product Key by itself, as they are normally stolen/pirated, Volume Licenses which are not for private use, or MSDN keys which are not to be sold by the original subscription holder.

Make sure that you buy the complete sealed package (DVD, license)