To get started developing with managed code, all you need is the .NET Framework Software Development Kit (SDK). This is available for free on MSDN (http://msdn.microsoft.com). In this download is the Redistributable, containing the CLR and the .NET Framework libraries, in addition to basic tools and compilers. Many developers will choose to use Visual Studio 2005 instead of simple SDK-based command-line development. Information on Visual Studio can be found also on MSDN (http://msdn.microsoft.com/vstudio).