To move an Exchange 2007 Unified Messaging server to new hardware, the account you use must be delegated the Exchange Organization Administrator role. For more information about permissions, delegating roles, and the rights that are required to administer Exchange 2007, see Permission Considerations.
See Unified Messaging Server Data, which covers what needs to be backed up on a Unified Messaging server, to make sure that you don’t have any custom settings that might be missed with the following procedure.