I would still recommend creating a new install set with the ""HTML Help Engine" checkbox checked. As I said, I had a very similar problem once that was fixed just by doing this. Maybe this time won't be the case but it might be worth a try ;)

>>We ran into that problem once. The way we fixed was rebuilding our application install disks with the Setup Wizard and checking the "HTML Help Engine" checkbox. Then, we reinstalled the application in the client machine and help started working.
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>I think that they've already got the help engine installed properly because Judy said that the help would come up if you double-clicked on the CHM file from Explorer. That was exactly what happened to me once, which turned out to be a problem with where the file was located.