You can change your login email address at any time in the Settings tab of the Account page. Please note that you can log in with any email address you have added to your account. However, if you no longer have access to an email address associated with your Facebook account, you will need to contact your email service provider in order to regain access to that address.
But it sounds like you no longer have access to the email address and so you may need to use the form here:
http://www.facebook.com/help/login.php