I have a user call me every morning to unlock his account on the domain. I told him to shutdown his PC before leaving office and I set him up just logon his computer account only, so that noone else can logon any other PC with his account. However, his account is still lock out every morning. I have no clue what cause of that, anyone suggest what utility tool monitor account lock status or resolve the issue?

Sounds as if someone is attempting to login to the Domain with this person's userid. Have you checked the logs on his client, or on your server to see what time this is happening? Life's more painless for the brainless.

You may need to enable auditing on logons/offs. Usual reason for such results is the users account is being used to run a service. User changed the password and now the account can't authenicate which locks out the user account. Imagine the power if you knew how to internet search