Outlook 2000 issue with logins

When logging to exchange via Outlook 2000 through a Cisco VPN, Some users Outlook does not rember the username or domain name. To clarify when you conect with the the vpn and open Outlok, Outlook promts the user with a login dialog requring a username, the domain name, and thier password. Some users Outlook remember the username and Domain name. some do not. What I want to know is how to make the systems which do not remember…remember.