Instructions
Turn on your console and log in to your Xbox LIVE account.
Press the guide button on your controller to call up the home menu.
Scroll to the settings tab of the pop-up menu.
Choose account management from the resulting list of settings options. The pop-up menu will close and an account management screen will appear.
Choose Windows LIVE ID from the resulting account Management menu.
Record your Windows LIVE ID email address from the right-hand pane of the resulting menu.
Navigate to Xbox.com on your computer, then select the sign-in link in the top right corner. This directs you to a page where you can sign into your Windows LIVE ID.
Click the blue "forgot your password" link. This directs you to a new page where you can begin to retrieve your Windows LIVE ID password.
Enter your email address into the corresponding text field, then enter the security characters into its corresponding field. Click to continue.
Choose to either reset your password via email or answer your secret question. Resetting the password via email sends a link to your provided email account to reset your password. Choosing the latter sends you to a page where you can answer your secret question that you chose when you set up the account. Answering the question correctly reveals your password.