Situation: Application was using .hlp file. User converted to windows 10 and help stopped working.

As is known, Windows 10 no longer supports .hlp files. I do not have access to the code for this production app. All I can do is change the file name being accessed (it's an ini file entry). The code uses the ShowHelp command with context sensitive indexing to go directly to the correct place in the help file using the windows title as the search key word.  Is it possible to simply convert the old .hlp file to CHM format?

What tool would I use to convert the .hlp file to chm? 

I've never had to deal with help files before and I've been doing this since version 2.0a.

So pardon my ignorance. Any help (pun intended) is appreciated.