Since there are directories all over the place for the Microsoft.NET Framework, I have decided to compile a list of some of the key ones used. Compilers, GACUtil, ASP.NET Register IIS/SQL, Assemblies etc. .NET 1.0: C:\Windows\Microsoft.NET\Framework\v1.0.3705 .NET 1.1: C:\Windows\Microsoft.NET\Framework\v1.1.4322 .NET 2.0: C:\Windows\Microsoft.NET\Framework\v2.0.50727 After 2.0, more directories were added, the build number was also omitted from the directory name. Some key utilities (for Global Assembly Cache (GAC), ASP.NET, Code Access Security Policy Tool (caspol.exe)) weren't part of future versions, so, as a result, .NET 2.0 is required by them. .NET 3.0 uses .NET 2.0 compiler. New directories: C:\Windows\Microsoft.NET\Framework\v3.0\Windows Communication Foundation C:\Windows\Microsoft.NET\Framework\v3.0\Windows Workflow Foundation (only SQL scripts in here) C:\Windows\Microsoft.NET\Framework\v3.0\WPF (Windows Presentation Foundation) C:\Program Files\Reference A