I don’t know how this happened.

One day, my help files refused to launch. Anytime I clicked on a CHM, nothing happened. I don’t know at what point it stopped working, and I don’t know what I installed to make it stop working.

Thing is, the components to launch a CHM file are part and parcel of the Windows operating system — there isn’t really an easy way to reinstall that particular portion of the OS without reinstalling the entire OS.

And my Googlefu was failing me — I don’t remember the search term I used to find a forum post that actually had a workable suggestion.

But I’m writing this post for posterity.

If your Windows help files don’t launch, download the MJS Diagnostic tool. The "Help Run-Time Components" section will tell you which files need to be installed and whether they are.

In my case, they were missing. I did hard drive search to see if maybe they were moved somewhere else. I found additional copies of those files in the C:\i386 folder, so I copied them to %WINNT%/system32.

After I did that, my help files could launch once again.

I’m glad I ran across this diagnostic tool, because I would have really tossed the curse words if I had to reinstall Windows just to fix my CHMs.