Windows 10: Not able to activate windows with product key

Hi,I had a windows 8 pro key which got automatically upgraded to windows 10 pro. I was using this key in my old desktop which was almost 6 years old. last year the desktop crashed. I bought a new assembled PC recently and I tried entering the product key I had for my old desktop. I am getting an error when I am trying to activate using that product key as it is saying invalid key.I tried reaching out to Microsoft support in India and they are pretty much helpless on this matter.I need to purchase a new key which is pretty expensive. Could anyone help me out here on what I can do as this was a

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Windows 10 product keys and activation - and the KMS angle

Changing the product key to the generic Windows 10 product key will reset activation to the standard retail channel for activation. It might just activate (if there was a previous digital license for Windows 10 for that computer established with Microsoft). Once Windows 10 is back on the retail activation channel, then more than likely changing the product key to the Windows 8 product key using the same method may work.

 

Activate windows 10 after re-installing (I have lost my product key)

I own a Lenovo T430 laptop. In 2017, I installed Windows 10 using my original Windows 7 product key. Unfortunately, I cannot find that product key anymore. I need to re-install windows 10. Will it be automatically activated after the installation, if I skip the step of asking the product key during the installation?

In my opinion, I believe that my laptop will have a digital entitlement stored on the Microsoft Activation Servers and this will not be a problem. Is that true?

If not, please suggest me a solution or a workaround.

 

Product key

Hi Megan,

A product key is used when activating a software.
To help us determine the appropriate troubleshooting steps that can resolve your concern, we'd like to ask the following questions:

• What product are you trying to activate?
• Are you looking for the product key to activate your Office application?
• Which version of Office are you trying to activate? To check this, you can perform the steps posted on this
  link.
• Are you looking for the product key to activate your Windows?

We look forward to your response.