You can use the Exchange Pre-Deployment Analyzer to perform an overall topology readiness scan of your environment. When you run the Exchange Pre-Deployment Analyzer, it provides a detailed report that will alert you if there are any issues within your organization, which could prevent you from deploying Exchange 2010. For example, the Exchange Pre-Deployment Analyzer will notify you if you haven't deployed the minimum required Exchange service pack on all your existing Exchange servers.
The checks performed by ExPDA are similar to the pre-requisite checks implemented (via Exchange Best Practices Analyzer) in the Exchange 2010 Setup program; in fact ExPDA is based off the Exchange Best Practices Analyzer (ExBPA) engine. However, unlike Exchange 2010 setup, this tool focuses only on overall topology readiness and not the ability to run Exchange 2010 on the local computer. The scan also performs a deep analysis of each existing Exchange 2003/2007 server to verify that it has the necessary updates and configuration in-place to support Exchange 2010. The end report is structured as follows:
Critical - A configuration problem that will prevent Exchange 2010 from being deployed in the organization. For example, the Active Directory Forest is not operating in Windows Server 2003 Forest Functional Mode or higher.
Warning - A configuration item that may prevent customers having the best possible experience with Exchange 2010. A warning may also reflect some functionality that is not available in Exchange 2010.
ExPDA is another component in our vision to provide a seamless upgrade experience that reduces the complexities in deploying Exchange 2010. To start planning your upgrade, please utilize the Exchange Deployment Assistant. The Deployment Assistant allows a customer to create Exchange 2010 on-premises deployment instructions that are customized to their environment. The Assistant asks a small set of questions, and based on the answers, it provides a finite set of instructions that are designed to get a customer up and running on Exchange 2010. Running the Exchange Server Pre-Deployment Analyzer is now a recommended step within the pre-requisites section of the Deployment Assistant.
For more information about ExPDA you can read the post wrote by the Exchange Team
You can download it here: