The answer, in case you didn't read the post subject, is Sandcastle. Sandcastle is a tool developed by Microsoft which builds MSDN-style help files by using reflection and XML comments from the source code of a project. Out of the box, Sandcastle is command line driven and kind of a pain to deal with, so I highly recommend the very easy to use Sandcastle Help File Builder (SHFB) application also hosted on CodePlex. This front-end provides a simple UI for setting options and building your help file in just a few minutes. The rest
Brian Peek's blog about game development, Azure, and other software & hardware stuffs.