I have a Dell inspiron N-4050 laptop. And i am running windows 10 pro on it. I have a product key for it and there was windows 7 genuine with the product key from the manufacturer. But now sticker with the product key on the back faded and no product key is there. I also change the Hard drive long ago. Is there any way i can find my product key for windows-7? Or I can give windows 10 pro product key in exchange with windows 7 pro of ultimate or any. Thank you.
In your situation, based on the comments, if you don't have the paperwork, there isn't a way to retrieve the product key.
If the machine had been upgraded, it would be possible to revert to Windows 7, then use a program such as Produkey to get the Licence Key from the system.