All Help files (*.chm) are corrupt

Whenever I try to open a Help file Vista gives me the message "..the
file is not a Windows help file, or the file is corrupted." This
message appears for every single help file I try to open.

I've tried setting the .chm extension to use both winhlp32.exe and
winhelp.exe but get essentially the same response from both.

I could not find anything in the MS Knowledge Base that matches this
problem. Google didn't help either. Where should I look for a solution?

-- .
Birk Binnard
http://www.birkbinnard.com

I lost the proper association for .chm files. The correct program to
open them is hh.exe, NOT winhlp32.exe or help.exe.

Re-associating the .chm extension with hh.exe fixed my problem.