You can search for a WinHelp decompiler on Google. It converts the .HLP file back to it's RTF source that you can then edit using a text editor or MS Word. You can find a .HLP compiler on the Microsoft website.
Or you can purchase something like Help and Manual, which includes a .HLP decompiler, an editor for help text, and can compile WinHelp and HTML Help, as well as produce PDF manuals, all from the same source.
You can search for a WinHelp decompiler on Google. It converts the .HLP file back to it's RTF source that you can then edit using a text editor or MS Word. You can find a .HLP compiler on the Microsoft website.
Or you can purchase something like Help and Manual, which includes a .HLP decompiler, an editor for help text, and can compile WinHelp and HTML Help, as well as produce PDF manuals, all from the same source.