A. The answer to this question varies according to the version of Exchange you plan to run. For example, Exchange Server 2003 runs on Windows Server 2003 and Windows 2000 Server with SP3 or later. Exchange 2000 Server runs on Win2K Server with Service Pack 1 (SP1) or later. And Exchange Server 5.5 runs on Win2K Server with any service pack and on Windows NT Server 4.0.
If you plan to run Exchange 2000, you don't have to install this version of Exchange on a domain controller (DC), although you can, but you must install it on a member server that has access to Active Directory (AD). Also be aware that the only version of Exchange that Windows 2003 can support is Exchange 2003. As a result, if you plan to upgrade from Win2K to Windows 2003, you'll need to upgrade to Exchange 2003 on Win2K before you upgrade the OS.