: Most computers from the Windows 7 era have a COA (Certificate of Authenticity) sticker on the bottom of the laptop or the side of the desktop tower. This sticker contains a 25-character product key that you can reuse to reinstall and activate Windows 7 Pro on that same machine.
These keys are often designed for trial periods or for switching between Windows versions; they typically will not activate Windows permanently. windows 7 pro product key free
: If you bought a digital copy, check the Microsoft account Order history for confirmation emails. How to Activate Windows 7 Without a Key (Trial Extension) : Most computers from the Windows 7 era