When launching Help within Visual Studio 2012 by pressing F1 or by choosing View Help (CTRL+F1) from the Help menu on the Standard Toolbar, you may encounter an issue where either of the following messages will be displayed:
Windows cannot find 'HlpViewer.exe'. Make sure you typed the name correctly, and then try again.
The Microsoft Help Viewer 2.0 or one of its components is missing or damaged.
To resolve this issue you should close all instances of Visual Studio 2010, open the Program and Features applet from the Control Panel, select the installed instance of Visual Studio 2012, select Change and proceed with the Repair option.
You may need to reset your personal preferences in the Tools, Options dialog as repairing an application overwrites those settings. It is suggested that you preserve your settings before proceeding with the Repair. From the Main Menu, select Tools and then Select Import and Export Settings...