Exchange Server 2007 Question:

If you are running 64-bit hardware in your current messaging environment, you may not have to buy additional hardware. However, Exchange 2007 does require hardware and an operating system that are 64-bit. 64-bit hardware provides the system architecture that is required to support the increased memory, storage, and enhanced security requirements in a more cost-effective manner. For more information about how to select the hardware for Exchange 2007