Windows 10: Reset then reinstall Windows 10 from Windows 7 laptop without keys

I have a laptop that was a Windows 7 and is now running Windows 10. If I want to sell, it how do I erase it but still retain Windows 10 when I do not have the activation key anymore?

:)

 

How to reinstall Windows 10 if my computers used the free upgrade from 7 and 8?

Will windows 10 still accept the license keys from 7 and 8 now if I reinstall my computer?

Does Microsoft keep a list of users who upgraded to Win 10 using their 7 and 8 keys so that when users need to reinstall windows 10 the old keys would work?

Do I need to call in Microsoft to ask them to activate my Windows 10 when I give them my win 7 keys?

Both computers are laptops. The windows 7 machine had the serial printed on the back, and I needed to enter that when I upgraded to 10. The windows 8 machine had the serial built in inside its boot system so I didn't need to enter the key when I upgraded to 10, but I did manage to write down the keys using a fetcher program.

 

Installing Windows 10 using Windows 7 key

Nope, you need to install Windows 10 first and make sure the Windows 7 key is transferred to your Windows account after you've installed Windows 10 (not quite sure how that works). I missed the last step and I could not activate Windows 10 after a re-install... Microsoft seem to have done everything they can to make it a PITA. Also, it's technically too late to do this now anyhow, as the upgrade offer has expired. But KMSPico works quite well...

As for getting rid of Windows, delete the Windows folder.

 

How to reinstall Windows 10 if my computers used the free upgrade from 7 and 8?

Your ild keys should work but if you registered the key to your online ms persona (email address) it should be tied to your account , install without a key login with your credentials , then activate.