Things You'll Need
Instructions
Turn on your Xbox 360, go to "My Xbox" and click "A" to sign in to your gamertag. Click "A" again once your avatar appears on the screen.
Click "Account Management" and select "Manage Account." Scroll over to the "Your Information" tab and click "Windows Live ID."
Click "Change Password" and enter your current password. Enter your new password, then enter it again for verification. Click "Change Now" to change your password.