Opening CHM Files in Vista

If any of you have been following me on Twitter recently, you know I’ve been researching the installation of TFS. I had pretty good luck with a lot of websites regarding TFS 2008, but not so much with 2010 Beta 1 (naturally). The only source for detailed documentation was Microsoft, so I went with what I had and downloaded the document. If you hadn’t guessed yet from the title of this post, the file had a .chm extension. After downloading the .chm file, I proceeded to open it. Much to my dismay, it opened but the pages would not load. I was getting 404 errors on every topic. After spending a few hours searching, I found a solution. Apparently the .chm extension is not secure and Vista removed the ability to read files like that unless they are in a specified safe location. I don’t particularly want to have to download any .chm file to an obscure location and then have to find that location again to open the file. Naturally, I searched for a simpler solution.

The solution I found, simpler or no, worked. You guessed it…it’s a registry hack.

I have a theory that one can literally do anything with registry hacks…things like make pigs fly or make hell freeze over.

Here’s what to do:

  1. Right click your .chm file and select Properties

  2. Click Unblock and select Apply

  3. Open up Regedit

  4. Modify the DWORD MaxAllowedZone to equal 1 (if it doesn’t exist, create it)

  5. Close all Internet Explorer Windows and start up your .chm file

That’s all there is to it. I haven’t had any problems with any .chm files since.