Windows Server 2003

Windows Server 2003 is the server counterpart of Windows XP. It comes in flavors of Datacenter, Web Server, Standard, Enterprise and Small Business (the latter is technically a separate version). It replaces Windows Server 2000 and was replaced by Windows Server 2008.

Codenames
Its internal codenames were either the dotNET (.NET) Server (As evidenced in the Windows Buildtree, where it's source is located at D:\dnsrv) and during the development of Windows Whistler (Windows XP), it was Code Named Whistler Server.

About R2 Version
An interim release was made, under the name Windows Server 2003 R2 on 2005-12-06.

Other versions
As well as the standard Windows Server 2003, several other editions were built on the NT5.2 kernel, including Storage Server 2003 R2 (released 2006-03-05), Compute Cluster Server 2003 (released 2006-06-09), Small Business Server 2003 R2 (released 2006-09-01) and Unified Data Storage Server 2003 (released 2006-12-05).

R2 RTM
This version is Windows Storage Server 2003 R2.

Compute Cluster Server

 * This is Beta Release for Compute Cluster Server.
 * This is Community Tech Preview, February 2006 for Compute Cluster Server.
 * This is the official RTM for Compute Cluster Server.