Windows Server 2003 R2 was an update of Windows Server 2003, rather than a "truly" new version of the operating system (as Windows Server 2008 R2 was). It went RTM on December 6, 2005, included a number of new features and was released for all editions and architectures supported by Server 2003, with the exception that Windows Server 2003 R2 Enterprise Edition was not released for Itanium.
- Improvements to the Branch Office management tools (DFS enhancements, Remote Differential Compression and centralized management tools for files and printers).
- New Identity Access Management functionality (Extranet single sign on, user access logging and web password synchronization).
- New File Management tools for SANs and file server, and improved quota management and file filtering.
- Better licensing terms for virtualization with Hyper-V
- UNIX utilities and SDKs for improved interoperability and development integration between Windows and UNIX systems.