The Microsoft .NET Framework is a comprehensive and consistent programming model. The .NET Framework is used to build applications that have a visually stunning user experience, seamless and secure communication, and the ability to model a range of business processes. The .NET Framework 4 works side by side with the older versions of the .NET Framework. Applications that are based on earlier versions of the .NET Framework will continue to run on the version that is targeted by default.
The .NET Framework 4 is available on Windows Update (WU) and Windows Server Update Service (WSUS). Specifically, the .NET Framework 4 is released as an optional update on Windows Server 2003, Windows Server 2008, and Windows Server 2008 R2.
On WSUS, the .NET Framework 4 is an optional update on Windows XP, Windows Vista, Windows 7, Windows Server 2003, Windows Server 2008, and on Windows Server 2008 R2.
For more information about the .NET Framework, click the following link to view the article in Microsoft Knowledge Base: