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:

![Windows 8 Activation Screen](https://i.stack.imgur.com/GaDQO.png)