You have installed a pirated version of Windows and you have decided to purchase a license of Windows and get on the right side of the law. But how to proceed? Re-install Windows and everything else (software, drivers etc)?
Download Key Update Tool, a utility provided by Microsoft to change the license key of Windows.
Launch the utility - the utility will then check the system files.
Enter the valid license key and click Next.
Accept the EULA and click Next.
Windows restarts and its legal.
You need to remember to activate your Windows license in order to qualify for updates. Activation request for Windows should be done via the Internet or by telephone. As a reminder, after 30 days without activating Windows, you can no longer use it.