One of the important aspects of migrating from one server to another is preserving mailbox information and other data. This technical article discusses Migration Wizard, which is a component of both Exchange 2000 Server Service Pack 1 (SP1) and Service Pack 2 (SP2).
Migrating Mailboxes from Exchange Server Version 5.5 to Exchange 2000 Server
Migrating Mailboxes from Exchange Server Version 5.5 to Exchange 2000 Server