By default, the Windows Server 2008 Default Domain Policy sets passwords to expire every 42 days.  This includes the built-in Administrator account as well if it has not been manually modified.  Changing the default administrator's password requires the extra steps described in this article to make sure that continuity is maintained between the services.

If you have not changed your password in the last 42 days, you will receive a login prompt indicating that you must update the Administrator's password[…]

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