CHM Files Not Working?

I ran into this the other day whilst on site, the symptoms typically include either “Page Cannot Be Displayed” or “Action Cancelled” errors when the user tries to run .chm files.

I discovered this has occured since the introduction of Security Update 896358 (June 2005). In all cases this occurs where the chm file is located on a server. Files on the users hard disk are not affected by this patch, so the first obvious workaround is to move the chm file! But there are other ways to fix this…

This is due to the way that Microsoft is tightening up security on the running of content hosted on other servers. If you ask me it is a total balls up, but Microsoft assure us it is supposed to be this way… Hmmm.

To fix this issue I did the following.

Locate the key:

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

Create a DWORD value called MaxAllowedZone and give it a value of 1.

This will enable Internet Explorer to load these files again.

Profile:  John has administered networks of various sizes for many years and also dabbles in PHP web development. More articles.