Backoffice 4.5 to Backoffice 2000

Hi all,
Currently , I only have a Backoffice 4.5 server in my firm. The setup is simple cos only 5 people are using this server for their mails/file storage. Recently , we bought a new server and we intend to install Backoffice 2000. I would like to know hot to migrate all the users to this new server, particularly , the Exchange settings.of the BO 4.5 server.

Please advice.
Thanks

Eric