The programming interface (API) in the client and server versions of Windows Vista. Originally called "WinFX" and superseding and backward compatible with the Win32 API, .NET Framework 3.0 is also available via downloads for Windows XP and Windows Server 2003.

.NET Framework 1.0 and .NET Framework 2.0 dealt with the Common Language Runtime (CLR) method of executing programs. .NET Framework 3.0 did not add major enhancements to the language infrastructure, but added the following four subsystems. See .NET Framework and Windows Vista.

The User Interface (WPF)
Windows Presentation Foundation (WPF) provides the user interface to Vista. It takes advantage of advanced 3D graphics found in many computers to display a transparent, glass-like appearance. See Windows Presentation Foundation.

Messaging (WCF)
Windows Communication Foundation (WCF) enables applications to communicate with each other locally and remotely, integrating local messaging with Web services. See Windows Communication Foundation.

Workflow (WWF)
Windows Workflow Foundation (WWF) is used to integrate applications and automate tasks. Workflow structures can be defined in the XML Application Markup Language. See Windows Workflow Foundation.

User Identity (WCS)
Windows CardSpace (WCS) provides an authentication system for logging into a Web site and transferring personal information. See Windows CardSpace.