CPS will work fine in a W2K enviornment backing up the Exchange server. Your issue really is the fact that the CPS console (the main portion of the program) is required to be installed on a W2K3 server. From there, you would push the CPS Agent (including the Exchange portion of the agent) to the exchange server (ie the Business server)
Just install CPS first on your Backup Exec server, assuming it is W2K3 and not on the Exchaneg server. From there, open the CPS console and push the agent to the exchaneg server. Afetr that is done, you can close the CPS conosle and never look at it again unless you are using it for other CPS work aside from Exchange. All CPS Exchaneg jobs are configured and maintained within backup Exec, BE just uses the CPS technology. CPS Console does not need to be setup to do CPS Exchange within BE.
Dave