Unfortunately there's no built-in tool in Windows Server 2003 that can let you dump all groups and their membership from Active Directory, though there are a few older Resource Kit tools you can fiddle with to do this e.g. showmbrs.exe, addusrs.exe and so on.
A better way of doing this however is to use DumpSec.exe, a tool available from SomarSoft at http://www.somarsoft.com.
Mitch Tulloch is lead author for the Windows Vista Resource Kit from Microsoft Press, which is THE book for IT pros who want to deploy, maintain and support Windows Vista in mid- and large-sized network environments. Mitch is also the author of Introducing Windows Server 2008, the first book from Microsoft Press about the exciting new server platform. For more information on these and other books written by Mitch, see www.mtit.com.