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Overriding the Default Viewer

posted Feb 11, 2010, 4:03 AM by Robert Chandler   [ updated May 29, 2012, 4:22 PM by Robert Chandler ]

This registry setting allows you to override the default viewer application used by MS Help Viewer (AKA Help 3) and VS 2010 IDE. 

Example 1: Set H3Viewer as the default viewer

HelpViewerProgID=c:\program files\Helpware\H3Viewer\H3Viewer.exe

Example 2: Set Google Chrome as the default viewer


Example 3: To return to the VS default viewer simply delete the registry value.


Normally when you (or VS 2010) ShellExecutes a ms-xhelp:/// help URL, HelpLibAgent.exe runs and launches the help in the defined browser.
Set this registry item to specify a different browser or viewer application to run.

In example 1 we specify that H3Viewer.exe is the default viewer. 

In example 2 we specify that Google Chrome is the default viewer (the path is for Chrome 4.x on a Windows 7 PC).

Note: Restart HelpLibAgent.exe once you change this setting.

  • To stop Agent right-click the Help Library Agent icon in the taskbar notification tray and select Exit.
  • To start Agent run "c:\program files\Microsoft Help Viewer\v1.0\HelpLibAgent.exe" <no parameters>
    Note #1: In the RC release there is a bug where Agent wont startup if Help Library Manager is set to "Online" mode. Try setting to "Local (Offline)" mode.
    Note #2: You don't have to restart Agent for dedicated Help applications such as H3Viewer. They will start Agent when they need to.