Can I move an existing Exchange Server machine to another server with a different name?
Not precisely. As you probably know, you can move Exchange to a different server with the same name by following the steps in the Microsoft article "XADM: How to Move Exchange Server to a New Computer with the Same Name" (http://support.microsoft.com/default.aspx?scid=kb;en-us;q155216). Such transfers are usually part of disaster recovery, although some hardy souls use this method when they upgrade to new hardware.
However, both Exchange 2000 Server and Exchange Server 5.5 encode the server name as part of the database, although in different ways—which is why you can't directly move the database files to the new server. You can always install the new Exchange server, then follow Ed Crowley's Server Move Method to move mailboxes, public folders, and connectors to the new server. (To obtain information about this method, go to http://www.exchangefaq.org and search for "Ed Crowley.") The Server Move Method helps you move to the new server without interrupting service on the old one.