I came across this today. If your app has .HLP format help files they will not run under Vista--unless your users download this program. Due to Microsoft's copyright I don't think you can distribute this exe with with your app so each user would have to download and install the help exe. Now would be a good time to convert HLP files to CHM.
James
WinHlp32.exe is required to display 32-bit Help files that have the ".hlp" file name extension. To view .hlp files on Windows Vista, you need to install this application.
http://www.microsoft.com/downloads/deta ... layLang=en