WinHlp32 and Windows 10
Windows 10 does not support .hlp Help files. Some older programs are still valuable, even if they are no longer supported by the developer, but if they rely on WinHlp32 then their Help files will not be accessible.
Fortunately, there is a work-around. In 2009, Komeil Bahmanpour wrote an excellent command file to install WinHlp32 under Windows 7 well before Microsoft finally provided an official download. Komeil maintains a blog on the WinHlp32 topic on his website   Although he has not yet released an update for Win10, his Win7 version will also work on Win 10 with a small change in the CMD file and the correct WinHlp32.exe version (it seems that not all versions of WinHlp will work). Visit the weblink for more information on this.
Komeil has a CAB file for download on his site which can be used after the CMD file is updated for Win 10. Once everything is set up with his file, installing WinHlp32 under Win10 is a simple task. As a convenience, this zipfile contains Komeil's command file which has already been modified for Win10 to disable the version check for windows 7, along with a copy of a working version of WinHlp32.exe. To install under Win10, simply download the zipfile and unzip it, then right click on the command file and run it as an administrator (for the necessary rights). Quick, simple and it works. Thanks to Komeil Bahmanpour and those contributing to his blog for this handy tool.
There are always potential security concerns that one should consider since this has been described as one reason why Microsoft changed from hlp to chm files. Some information on this can be found in the WinHlp Wikipedia article. However, WinHlp32 is probably no riskier than other executables, and the only other recourse for abandoned programs may be to decompile the .hlp files and recompile as chm which has a number of limitations also.
Information on the files included in the zipfile is given below. The MD5 and SHA values provided in this description can be validated online at various locations.
Zipfile information: Contains WinHlp32.exe , winhlp32.exe.mui, and install.cmd . The data for the two binary files are as follows:
WinHlp32.exe file size on disk: 296,960   Version: 50.0.6000.16387   02/19/2007
WinHlp32.exe.mui file size on disk: 31,744
Obviously Komeil's CMD file can be read directly as simple text. Incidentally, these codes were generated with QuickHash 2.6.7.
The latest version of QuickHash is available here:   Hashcodes