Bop up Messenger service on LAN help reqd

I m handling a LAN of 35 computers placed at separate locations and I m trying to load a messenger service avbl as freeware. I tried Bopup Communication Server with Bopup messenger as the solution from bell labs but once installed on the LAN. The messeges sent to the whole domain or @ALL are delivered but the moment I try to send message to a particular user or computer the message comes that the user not avbl do u want to store the message on comm server and after some time the server is also not found. :roll: I tried file transfer also but the error is the computer/user name not resolved. However the Bopup scanner scans the network all the computers with the users logged on them correctly. I have a Client server configuration with win 2003 server and win 2000 pro/ win XP clients.....
Can anyone help me on this? I posted my problem to Bell Labs to no replies. And the online help says to start BCserver in services menu on the Bopup Communication server computer but on my server this option is not available at all.......