Background

For the last several months, I have not been able to open .chm files that I copied down to my local box. Not sure exactly when it started happening, but my guess is after a windows update in the last couple of months. I am familiar of the changes to the .chm file behavior in XP SP2, (security update 896358 or Windows Server 2003 Service Pack 1) as described in KB 90225. Didn't see to be related to this.

When I would click on the file and tried to open it, I would get the HTML Help window up and a File Download - Security Warning dialog asking me to Open, Save, or Cancel.

If I click Open, 

I get a File Download dialog, then it goesback to the HTML Help and File

Download -Security Warning dialogs. An infinite loop.

If I Click Save,

I get the standard Save As dialog, and I save to another

location and try to open it there, I get the infinite loop above again.

No one else was seeing it in the office, then I narrowed the problem down as it looked as if it followed me around with my AD account. If I logged on to any other machine, I could not open at .chm files. All other users w/ accounts on the machine could as long as they were not in any of my directories. Happens on XP and Vista Operating Systems.

Finally, it dawned on me. My domain account is Domain\Tom.Chmielenski, notice the .chm characters. Tried my wife's account. Wha La! She has the same Problem. With the help of my colleague, Jason, we were are able to narrow the problem down to a simple problem. The problem has been sent to Microsoft.

Summary of the problem

.CHM files can not be opened if the filepath includes the [.chm] characters within it.

Very easy to reproduce the problem

1.     Make a directory C:\TEST_CHM,

   [Syntax is TEST {UnderScore} CHM]

2.     Copy any .chm file to this new directory.
3.     Launch the .chm file (it will work fine)
4.     Rename c:\TEST_CHM to be c:\TEST.CHM

   <!-- Syntax is TEST {Period} CHM] -->

5.     Try to open the .chm file. (it causes an infinite loop).

      

Workaround

Copy the .chm file to a different directory where the .chm is not in the path.