That screen pretty much sums it up for how the "specially marked boxes" of Crackdown are going to allow downloading the Halo 3 Beta. Simply navigate to the "Downloads" section in the menu, and there's an option to get the Halo 3 Beta. We presume that an Auto Update will take place on the beta's launch and then the message at the bottom of the screen will change appropriately. So, while a bunch of fanboys eagerly await halo3.com to allow them to register, at least they can get a glimpse of their next and final option available in just of 2 weeks.
Update: The hosehead blogger responsible for crediting the wrong source has been reprimanded accordingly. Not only was he subjected to 360 lashes by strips of Canadian Bacon, but his following paycheck will be using an embarrassing 1:1 USD/CDN exchange rate.