The .NET Framework 3.0 has been created mainly as an extension of .NET 2.0. Hence, Microsoft assures us that most of the features of .NET 2.0 would be workable with .NET 3.0. Migration from .NET 2.0 to .NET 3.0 is easy as it involves only the upgradation of the features and not a complete installation of the .NET 3.0 framework. Applications written and run in .NET 2.0 will still continue to run in .NET 3.0 without affecting the execution of .NET 3.0 specific applications.Components shared with the .NET Framework 2.0 are installed at %windir%\Microsoft.NET\Framework\V2.0.50727. Components that are new to the .NET Framework 3.0 are installed to %windir%\Microsoft.NET\Framework\V3.0.
Released on November 6, 2006, .NET Framework 3.0 was designed to be shipped as an integral part of Windows Vista Operating System and Windows Server 2008 . Nevertheless, .NET 3.0 also works fine with Windows XP and Windows Server 2003.
.NET 3.0 does not contain any major architectural change from .NET Framework 2.0. The only significant chage is the inclusion of four major components: Windows Communication Foundation, Windows Presentation Foundation, Windows Cardspace and Windows Workflow Foundation. These components contain modules of code in order to reduce complexity and to make programming simpler, faster and easier.
.NET Framework 3.0 includes version 2 of the Common Language Runtime(CLR).
A better idea of the .NET Framework can be obtained by visiting the official .NET 3.0 site www.netfx3.com.You can experience for yourself the features of .NET Framework 3.0 by registering and using Windows Vista simulations at Microsoft .NET 3 Virtual Labs