Click the Start button (Windows logo) at the bottom left of your screen.
Scroll down to the bottom of the System window that appears. Look for the section labeled Windows activation .
Right-click on cmd.exe in the search results and select Run as administrator . Click Yes on the User Account Control prompt.
There are three reliable methods to change your Windows 7 product key. Below, we break down each one, from the simplest graphical interface to the command line. This is the most common method for average users.