To use Windows Messenger in a local environment (that is, without internet access), you'll
need a local Exchange 2000 IM server or Live Communications Server.
However, keep in mind that Windows Messenger is a discontinued product. The successor is
Office Communicator which requires Office Communications Server.
None of these solutions however are free (or really even cheap).
--
Jonathan Kay
Microsoft MVP - Windows Live Messenger
MSN Messenger/Windows Messenger
MessengerGeek Blog: http://www.messengergeek.com
Messenger Resources: http://messenger.jonathankay.com
(c) 2008 Jonathan Kay - If redistributing, you must include this signature or citation