Can we use Windows 7 without product key?

No, you cannot use Windows 7 without a product key. The product key is a unique alphanumeric code that is required to activate and validate the operating system. It is necessary to prove that you have a genuine copy of Windows 7. Without a valid product key, Windows 7 will enter a limited functionality mode, where certain features and updates will be disabled. To fully utilize and legally use Windows 7, you must have a valid product key.

It is possible to install Windows 7 without a product key, however, it will only be a trial version and will require activation within 30 days. During the installation process, you will be prompted to enter a product key but have the option to skip it.