To Change a Product Key in Vista/ 7 OS Follow these simple steps. 1. Click on Start Menu 2. Click on Control Panel 3. Click on System 4. In the bottom where it says Product ID next to that you will find a link which says Change product key, click on that. Alternative method to Change Product CD Key in Windows 10, Windows 8/ Windows 7/Windows Vista 1. Click on Start menu. 2. right click on My Computer and select Properties. 3. In the bottom where it says Product ID next to that you will find a link which says Change product key, click on that. On Windows 10 To Change a Product key on Windows 10 Follow the following steps: 1. Click on Start Button 2. Highlight File Explorer, Right Click on it and Select Properties 3. In the System Properties window, on Bottom-right corner, there is option to change the Product Key!