CHM files: Page cannot be displayed

I'm not sure if this was related to my recent install of XP SP3 (I haven't done anything else of note recently...), but I found out today that I was unable to view CHM files on my system. Most of my manuals are stored in CHM format, so, this was something of a pain. While the file itself opened fine, and the content list pane was accessible, the content pane was not; I instead was greeted with a "The page cannot be displayed" error message.

Googling around led me to this M$ KB article which detailed the following fix along with a plethora of warnings:

1. Open up notepad.
2. Copy and paste the following:

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

3. Save the file on your desktop as something like chmfix.reg.
4. Double click the file on your desktop to merge new settings into your registry.
5. Test your CHM file, and you will very likely find that it's been fixed.

As the knowledge-base article repeatedly states, doing this also lowers the security of (IE in) your system; i.e. this was actually done for a reason. You might want to read through that KB article and also use UrlAllowList to reduce any side-effects. You will also very likely want to only apply the above fix after exhausting all other avenues. Bewarned :)