Sandcastle is a free Microsoft tool that automatically generates documentation from program source assemblies and XML comment files for Microsoft Visual Studio .NET development projects. If you are already using Sandcastle and have it installed on your computer Help+Manual supports it from version 2.4 and above. However, we strongly recommend installing the runtime version bundled with Help+Manual. It is the latest official version from Microsoft and will be used automatically once it is installed.
Help+Manual comes with the latest official version of Sandcastle from Microsoft. You just need to select the Sandcastle option when you install Help+Manual to get it. We strongly recommend using the bundled version. It is the latest available and Help+Manual is optimized for interaction with this version. It will not interfere with your own Sandcastle installation if you have one, but once it is installed Help+Manual will only use this version and will ignore your version.
If you didn't install Sandcastle with Help+Manual just run the latest installer again and select the option shown above. For more background information about Sandcastle see Microsoft's Sandcastle page.
Microsoft is no longer releasing new versions of Sandcastle (but that doesn't prevent it from working just fine). There is now an independent project called Sandcastle Help File Builder, developed and maintained on Codeplex by Eric Woodruff. You don't need to use Sandcastle Help File Builder with Help+Manual, and it is also not possible to do so. It is not needed because Help+Manual performs the tasks that HFB performs, interfacing with Sandcastle and generating the output.
You are free to use Help File Builder with your Sandcastle installation independently of Help+Manual, of course. You just don't need it and can't use it for generating Sandcastle source code documentation from your .NET projects with Help+Manual.