This has yet to be confirmed, but the rumour is that if you have a DVD Drive in your PC you can put the Episode-I DVD in and in the menu will be an "Exclusive Web Link Content" button that takes you to a restricted area of the StarWars.Com website.
Whilst the weblink has been confirmed to exist by various reviews, there is no content yet so no one knows what will be there.
The hope is that it will be the episode-II trailer, but who knows.