Download WinHlp32.exe, to view older Help files on recent Windows
Windows does not support older help files (*.hlp), unless you download Windows Help (WinHlp32.exe), a Help program that has been included with Microsoft Windows versions starting with the Microsoft Windows 3.1 operating system.
The Windows Help program has not had a major update for many releases and no longer meets Microsoft’s standards.
Therefore, starting with the release of Windows Vista, the Windows Help program will not ship as a feature of Windows. If you want to view 32-bit .hlp files, you must download and install the program (WinHlp32.exe).
Instructions: extract the zip archive anywhere and run the install.cmd file — or try running the .msu file to let the OS handle the setup.