Change the Windows 8 product key after installation?

I just completed a fresh install of Windows 8 Pro as it was released to MSDN. Installation went without a hitch however I can't find out where to enter the correct product key for the copy I have.

Clicking on the Activate this Computer in Activity Centre displays the following screen, but no option to change the product key:

Just follow these steps to add/change product key using Command Prompt and slmgr.vbs:

1. Launch Command Prompt as an Administrator.

2. At the command prompt, type in slmgr.vbs -ipk(insert your product key here) and click Enter.

3. To activate windows, type in slmgr.vbs -ato and click Enter.

All information form this Source

The command to display the GUI for changing the product key is slui 3 (you need to run the cmd.exe as an administrator).