Visual Studio 2010 includes a taskbar applet in the Windows notification area (system tray) that arbitrates between viewing offline help and online help in the browser when F1 is pressed, and resolves help topic URIs to the proper topic page.
Microsoft Help Viewer 2.0 uses a COM runtime library, so the taskbar applet is no longer used.
[1] The runtime API is accessible via .NET dlls used in VS2012 and Windows 8; they are equivalent except for a name change.
[2] VS2012 ships a more sophisticated toolkit (HlpViewer and HlpCtntMgr), while Windows 8 only has a one-pane HelpPane program.
Special meta tags are provided for navigation, and there is support for signing the help bundle.