Instructions
Go to the Xbox website (see Resources) and click the "Support" link at the bottom of the page.
Click the "Register and repair your product" link under "Services," which is under the Xbox 360 picture, to open the product-selection screen.
Click the "Register" button to access the account log-in or creation screen. Log into your Windows Live account or create a new account.
Enter your country, name, address, telephone number and e-mail address in the fields provided.
Locate the serial number printed on a white bar-code sticker on the back of the Xbox 360 Elite. Enter it in the "Serial Number" field and click "Submit." Your 360 is now registered.