winhlp32.exe should have shipped with Windows Vista and it should live in C:\Windows.
Best advice would be for them to find a different program that is supported for their job. Almost anything has some comparable replacement.
Thanks for taking the time to reply, but you need to read my query more carefully. The particular situation I described is not covered by your answer.
First, my friend has a very specialized program used by certain academics in the humanities, and to use the program effectively, he *must* have access to its help files, and that means he *must* have the winhelp32.exe file *working* on his Vista system. There is no easy substitute for this program, and the substitutes out there cost over a thousand dollars.
Second,
no, the old help file reader did *not* come loaded with the Vista system, but had to be *added* as an update later. (Users of Windows 95, XP etc. squawked about not being able to use their old programs, and so Microsoft made a patch/update available for Windows Vista, 7, and 8.) Unfortunately, just when my friend was going to download the patch/update, Microsoft ended all support for Vista, and that meant no more downloads of the update that would enable old help files to work with Vista.
Third, as I said, my friend now has (from a third party source) *the exact help file that would have been downloaded on an official Microsoft update*, but it's sitting as a download, not integrated with his Vista 32 system, and therefore he still can't read the help files. What he needs is a person who works for Microsoft, or used to work for Microsoft, to be kind enough to tell him the steps -- which may be very simple -- needed *to get the downloaded file working on his system*, so that he can read help files in his old programs. In other words, my friend is trying to accomplish what would have been accomplished automatically if Microsoft was still offering downloads of the update/patch. Because he did not get the file from Microsoft, it isn't integrated into his system the way it would have been had he been able to do the official download. If anyone out there is old enough to remember how Vista downloads coming from Microsoft worked, and would pass along the information for how to do this, I would be grateful.