TechNote 10009: HTML Help files will not open across the network

After installing recent Microsoft security patches you may find that HTML Help (.chm) will not work across the network. You will know this is a problem when you load your help file because the table of contents will display but on the right where your topic should be it will say "action canceled" as shown in the example below.

There are a couple of ways to work around this problem.

Option 1 - Lower security

You can use certain registry settings to tell HTML Help to ignore the security restrictions. This is reasonably easy to do http://support.microsoft.com/kb/896358 contains details of the restrictions and what you can do.

There are basically two possibilities:

1. Allow all chms on your intranet to run

This is not particularly restrictive but if you are confident of the security on your network this would work fine.

REGEDIT4

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp\1.x\HHRestrictions]

"MaxAllowedZone"=dword:00000001

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp\1.x\ItssRestrictions]

"MaxAllowedZone"=dword:00000001

Download this example as a .reg file.

2. Allow specific folders

In this case you restrict the ability to display chms to a specific folder. This is quite restrictive but would work fine if you are only needing to run chms from a specific place. In some cases such as the root folder of a drive limiting it to a folder doesn't seem to work. In the example below you want to allow access to any HTML Help files in the folder \\server\data

REGEDIT4

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp]

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp\1.x\HHRestrictions]

"MaxAllowedZone"=dword:00000000

"UrlAllowList"="\\server\\data;"

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp\1.x\ItssRestrictions]

"MaxAllowedZone"=dword:00000000

"UrlAllowList"="\\server\\data;file://\\server\\data"

Download this example as a .reg file.

Option 2 - Use BrowserHelp

This option is just a change of target so rather than outputting to HTML Help you output to BrowserHelp. BrowserHelp is a browser based help system so it will work in any browser. It gives you most of the functionality you are used to in HTML Help, such as table of contents, index and full text search.

Rather than linking to a chm file you simply link to the home page of your project (such as index.htm) and now your content will be able to be displayed across the network.