Today, Microsoft opened up registration for the preview program for this fall’s dashboard update. This update includes ESPN, Netflix search, the new dashboard, and updates Zune and family settings.
All you have to do is go to Microsoft Connect through this link, sign in with your Windows Live ID that’s connected to your gamertag, and fill out the form. You’ll be notified immediately if you’ve been selected.
Make sure you have your Xbox 360 serial number and console ID handy. To find those from the dashboard, go to My Xbox, then scroll to the far right to System Settingsand select it. From there, select Console Settings, then System Info.
Good luck!
Source: Major Nelson