Hi Chris
I'm Wilfredo S an Independent Advisor
According to what you describe and the known information The full format name of the files that use the HLP extension is Windows Help Format.
Microsoft defined the Windows Help Format standard. HLP files are compatible with the software applications available for devices running Linux, Mac OS, Windows.
The HLP file belongs to the category System Files as well as 298 other file name extensions listed in our database.
The most popular program for handling HLP files is Adobe RoboHelp, but users can choose from 8 different programs that support this file format. The software called Adobe RoboHelp was created by Adobe Systems Incorporated.
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Unfortunately, the HLP files generated for older versions of Windows are not always displayed correctly in the Windows help viewer of the most recent installations.
In the following link you have some suggestions on how to convert the file
https://windowsreport.com/open-hlp-files-window...
and
https://www.tenforums.com/general-support/16982...
Note: This is a non-Microsoft website. The page appears to be providing accurate, safe information. Watch out for ads on the site that may advertise products frequently classified as a PUP (Potentially Unwanted Products). Thoroughly research any product advertised on the site before you decide to download and install it.
I hope it helps you