How to Open help (.chm) files over unc path

Solution 1:

See KB article http://support.microsoft.com/kb/892675/ which includes detailed explanation of the issue, examples and methods for deploying changes across your domain. I've copied a couple of examples below for reference.

If you want to permit opening of all CHM files in the "Intranet" zone, then the following registry entry will do the trick.

REGEDIT4
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp]
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp\1.x\HHRestrictions]
"MaxAllowedZone"=dword:00000001

If you want keep things more secure and only permit access to CHM files on a certain UNC path, then use the following instead replacing \\productmanuals\helpfiles with the UNC path that you want to allow (don't forget to use double backslashes)

REGEDIT4
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp] 
[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp\1.x\HHRestrictions]
"UrlAllowList"="\\\\productmanuals\\helpfiles"

Solution 2:

See this KB article: http://support.microsoft.com/kb/896358