http://support.live.com - it will be an email form. If your account got locked out, it will unlock within 24 hours. However, if you don't recall the password, you will need a reset which can be done from http://account.live.com assuming you set up an alternate email address and/or the secret questions. If you didn't, use the support link above, select Windows Live Account. You will get an email response with questions to prove that the account is yours.
-steve