Instructions
Navigate to Halo 3's main menu on your Xbox.
Select "Theater."
Select "Start" to bring up a new menu.
Select "File Share." A menu opens with a number of open slots for images.
Select one of the open slots. A new menu opens, asking "What Do You Want to Share?"
Select "Screenshot." Your saved screenshots will appear on the screen.
Select the shot you want to move to your PC, and it uploads to your Xbox Live account.
Navigate to Bungie.net on your computer.
Log in to your Xbox Live account using the "Sign in" link in the screen's top-right corner.
Accept the Bungie terms of agreement.
Click the "Profile" link.
Click the "Online Stats" link.
Click the "Screenshot Gallery" link.
Click the "File Share" tab.
Right-click the screenshot you want to save. Select "Save Image As" to copy it to your PC.