If you don’t have a product key, there are several legitimate options for activating Windows. You can purchase a genuine license from Microsoft’s official website or authorized retailers. Alternatively, if you qualify, you might be able to upgrade to Windows 10 or Windows 11 for free using the Windows Update tool, especially if you’re upgrading from a previous genuine version of Windows. Additionally, educational institutions sometimes provide discounted or free licenses to students. Always choose legal methods to ensure that your software is properly activated and supported.