When a domain controller goes offline or isn't accessible, a number of previous logins are cached at each NT workstation. However, this is a potential security risk because users who have been removed from the primary domain controller (PDC) can still log in to previously logged workstations by disconnecting the machine from the network.
By default, the last 10 logins are cached on the local system. To close this security hole, disable login caching. Here's how:
You may want to reconsider disabling cached logins on notebook or traveling systems since this feature allows the administrator to support resources centrally, without having to maintain a user database on the local system.
Note: Editing the registry is risky, so be sure you have a verified backup before making any changes.