Instructions
Turn on your Xbox 360 and wait for your dashboard to load.
Press the "Xbox" button in the center of your controller. This will load your Xbox Guide
Press "Right" on your controller, go to "Settings" and choose "Account Management."
Select "Windows Live ID" and "Change Windows Live ID."
Enter the Windows Live address you want to link to your account. Press "Start" on your console. This will set the email address to your Xbox LIVE account.