Using HelpViewer local or try to Add or Remove Content from the VS2012 Help Menu always results in message:
The location you specified for installing Help content is invalid, or you do not have permission to access it.
I get the error using using VS2012 Update 3 as an admin, or using command line HelpViewer as admin.
So I think this is a 'specified location invalid' not a permissions problem. I check the registry, and
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Help\v2.0 AppRoot is C:\Program Files (x86)\Microsoft Help Viewer\v2.0\
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Help\v2.0\Catalogs ContentStore is C:\ProgramData\Microsoft\HelpLibrary2\Catalogs\
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Help\v2.0\Catalogs\VisualStudio11\en-US catalogName is Visual Studio 2012 Documentation
And the MSHC and METADAT files are installed at C:\ProgramData\Microsoft\HelpLibrary2\Catalogs\VisualStudio11\ContentStore\en-US
There is a discrepancy: what is the CatalogName? is it "VisualStudio11" or is it "Visual Studio 2012 Documentation"?
I even tried to repair VS to fix. First I used Control Panel Programs to remove HelpViewer 2.0. then I repaired VS 2012. The removal removed the HelpViewer app and files, and the repair restored them. I don't recall and did not note (my bad) changes to registry. But same ugly issue.
There are few related posts on the Internet, but I cannot find complete definitive information about the registry settings in relation to content and exe location
I finally found the registry documentation for Help Viewer 2.0 at:
http://msdn.microsoft.com/en-us/library/hh500508.aspx
I solved the problem by Editing:
HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\Microsoft\Help\v2.0\Catalogs\VisualStudio11, setting the Key, LoactionPath, to the Value, C:\ProgramData\Microsoft\HelpLibrary2\Catalogs\VisualStudio11
Note that the .mshc, .mshi, .metadata files are located at: C:\ProgramData\Microsoft\HelpLibrary2\Catalogs\VisualStudio11\ContentStore\en-US