To recover your account information, go to http://www.livejournal.com/lostinfo.bml and follow the instructions given there. Your information will then be mailed to you.
For security reasons, LiveJournal will only send your password to an email address that has been validated for that account. If you no longer have access to a previously validated email address, you will not be able to recover your username or your password.
This is an automated process and, as such, LiveJournal staff and Support volunteers do not have access to your password and will not be able to provide it to you.
If you can no longer access a validated email address and have forgotten your username or password, you may create a new journal. Invite codes will not be provided for this purpose. See http://www.livejournal.com/support/faqbrowse.bml?faqid=104 for instructions on creating an account.