System Center Capacity Planner 2007 is a pre-deployment capacity planning and post-deployment change analysis solution that provides best-practice guidance and hardware-specific knowledge to help information technology professionals make solid architecture decisions when planning a new deployment or changes to an existing deployment for Microsoft Exchange Server 2007 and other Microsoft server products as add-in application models become available.

http://www.microsoft.com/downloads/details.aspx?FamilyId=E754F35D-59DB-4BC4-8386-E83E66A16FAD&displaylang=en