Before you install Exchange Server 2003, ensure that your network and servers meet the following system-wide requirements: Domain controllers are running Windows 2000 Server Service Pack 3 (SP3) or Windows Server 2003. Global catalog servers are running Windows 2000 SP3 or Windows Server 2003. It is recommended that you have a global catalog server in every domain where you plan to install Exchange Server 2003. Domain Name System (DNS) and Windows Internet Name Service (WINS) are configured correctly in your Windows site. Servers are running Windows 2000 SP3 or Windows Server 2003 Active Directory.