I take it you mean Outlook Express. This may help - enter link description here
OR - What you'll have to do is to call up your Internet Service Provider. Once you provide them with your phone number, or account number, and they verify that you are the primary account holder by asking a couple of security questions, they'll be able to tell you what the username (e-mail address typically) and password associated with that account is. This is the info that Outlook Express needs in order to successfully send/receive e-mails for you.