Visual Studio 2012 help Viewer broken, how to reinstall?

Question

I have uninstalled Help Viewer 3 of VS 2012.

Now I want to reinstall it, but I don't know how.

Using add/remove program, and "Modify" VS 2012, there is no option to reinstall the help.

A repair of VS 2012 does not install the help.

If I launch from the VS DVD image the file Packages\Help\help3_vs_net.msi, it says that

This component may only be installed during Visual Studio setup.

How can I force the reinstallation? Is there any switch to pass to msiexec to workaround the issue?

[Edit] A bit of progress, according this thread, I can run msiexec /i help3_vs_net.msi VS_SETUP=1. This installs the help viewer.

Unfortunately, when I start it, it says :

A content file required by the Help Viewer is missing or has been corrupted.

Answer 1

This message is usually found when the content store for the Help Viewer has been moved and the registry key is pointing to the wrong location, as seen here.

Please try to change your registry key 'LocationPath' under the folder below to the correct folder where you moved the content store to.

HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Help\v2.0\Catalogs\VisualStudio11

(you can probably find the folder by searching for the file CatalogType.xml)