I have been tasked with taking an existing Exchange Server 2007 installation and clustering the mailbox role. Currently, all roles are installed on one server. What will I need to do to move the mailbox role off of this server and making it an active clustered role? I understand that the mailbox role has to be the only role on the server if I want to use CCR. I will also need to add a passive role as well but I assume that's going to be pretty straightforward once I get the active role installed and working.

You need to install the active and passive node of the CCR mailbox cluster from scratch into your Exchange organization. Neither Hub Transport nor Client Access server role can reside on the CCR cluster. Move all mailboxes (and public folders) from the existing mailbox server to the CCR cluster. De-install (remove) the mailbox server role from the first mailbox server and leave the Hub and CAS installed. These are the basics. (You can later add a second Hub/CAS server and cluster the CAS server with NLB and to a limited extent the Hub server (mostly for internal SMTP).jas