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CHM help file shows error messages instead of help pages
Hilmar Zonneveld, October 6, 2005
Due to a recent Windows security fix, users can no longer access a CHM file on a server. The table of contents appears, but the individual pages are replaced by error messages. Access to CHM files in specific folders can be explicitly allowed through special registry settings.
Summary
Due to a recent Windows security fix, users can no longer access a CHM file on a server. The table of contents appears, but the individual pages are replaced by error messages. Access to CHM files in specific folders can be explicitly allowed through special registry settings.
Description
Description: This information is gleaned from knowledge-base articles, and UT discussions. Symptoms: When viewing a CHM file, users see the table of contents, but the individual help pages are replaced with an error message that looks like a standard IE "page not found" error. Cause: This is caused by a recent security patch; it was discovered that CHM files can carry malicious code, so access to CHM files in remote locations is disabled by the security fix. Solution: Knowledgebase articles mention several workarounds; amongst others, the security patch can be disabled, or the CHM file can be copied to a local drive. The first solution is dangerous. The second requires some coding to check for, and copy, the latest version of the help file or files, but it is quite feasible. You can also permit access to CHM files in a specific folder, with specific registry settings. This is the method I will explain in more detail. Create two text files, one called enablehelp.reg, and one called enablehelp.bat, and place them in the same folder. Write the following text into the .BAT file: 
regedit.exe /s enablehelp.reg
Write the following text into the .REG file: 
Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\HTMLHelp\1.x\ItssRestrictions]
"UrlAllowList"="\\\\myserver\\myapp\\help;file://\\\\myserver\\myapp\\help"
Adapt the name of the server and path that contain the help file or files. Note that you need to replace each backslash, "\", in your path, with a double backslash, "\\". Place both files in a shared folder, and instruct the users to run the batch files. (You can omit the batch file and run the .REG file directly, but that will require an additional confirmation from the user.) Some knowledgebase articles also mention ways to fully automate this, through group policies, but I didn't investigate this in detail. Further information http://support.microsoft.com/kb/896054/ and related links.
Hilmar Zonneveld, Independent Consultant
Hilmar Zonneveld works in programming since 1986, using dBASE, FoxPro and Visual FoxPro. He is available as an independent consultant. He currently works as a programmer at Bata Shoe Organization; also as an instructor at Cisco Networking Academy. You can contact him through the Universal Thread, or, via e-mail, at hilmarz@yahoo.com. Personal Web page (mainly in Spanish): www.geocities.com/hilmarz.
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