Your Windows 10 product key serves as proof that you actually own Windows 10, and might need to be entered when you reinstall or upgrade Windows.

Lost your Windows 7 product key? Use this quick guide to recover it from stickers, emails, tools, or Microsoft Support.

Usually, you'd activate Windows 11 (or 10) using the Settings app to enter the product key. However, if you're in an enterprise environment and you have a specific type of activation key, you can also ...