The Web.config is an XML based configuration file for the entire application and resides in the application root. It provides the application wide settings for the entire application. The Machine.config located at the "C:\WINDOWS\Microsoft.NET\Framework\vx.x.xxxx\CONFIG" directory, is used to apply configuration settings for any applications that are running in the entire system. In my system with .NET Framework 1.1 installed, it is located at the "C:\WINDOWS\Microsoft.NET\Framework\v1.1.4322\CONFIG" directory. This article discusses both and shows how we can use them in our applications. Note that I have discussed the most important sections in these files. I would request the readers to refer other reference materials for a complete reference on these files.