To reset your account information on an Xbox 360, go to Microsoft's Xbox support website at support.xbox.com. From there, select Xbox 360 and then click on the My Account link on the left side of the page. You may then choose to recover or reset your account information.
If you are unable to remember the password for your account, you may now follow the steps to reset your password. From here, you are asked to select the reason you cannot access your account, such as having forgotten the password or suspecting that someone has taken control of the account. Microsoft then sends you a text message or an email containing your new password.
If you have forgotten the email address you used, you may select that option under Xbox 360 support instead of resetting your password. The method that you use to recover a lost email address differs depending on your situation. Factors include whether the account is a "Child" account or an "Adult" account and whether or not you are using a computer or your Xbox 360 console to complete the recovery. The recovery process is typically quicker to complete on a console than it is on a computer.