Things might have changed by now, but it took me 4 days before I got my Free Media Center Key, but did get it.
◄ § ►
Getting the Free Product Key
Once you access the above website, provide a valid email address in the relevant box. It takes 24 hours for you to receive your free product key. This will be through the email address you provided.
(http://i50.tinypic.com/2dsisgk.jpg)
(http://i47.tinypic.com/34srps1.jpg)
Tip! Don’t forget, you can only receive one copy per Microsoft Account. This was my error .
Installation Procedure
Follow these instructions for adding Windows 8 Media Center Pack.
(http://i47.tinypic.com/rhqw7r.jpg)
Note: If running Windows 8, your PC will restart automatically and Windows 8 Pro with Media Center will be listed in the Metro screen.
(http://i48.tinypic.com/ojjxtu.jpg)
Tip! Consider “pinning” the Media Center to your Desktop’s Taskbar! To do this right click and select Pin to Taskbar.