Old .hlp (Windows help) files cannot be natively opened in Windows 7. Although Microsoft offers winhlp32.exe for the Windows 7, it generally displays the following message when attempting to open .hlp files:
“The Help for this program was created in Windows Help format, which depends on a feature that isn’t included in this version of Windows. However, you can download a program that will allow you to view Help created in the Windows Help format.”
Fortunately, Komeil Bahmanpour has patched together a solution that can open these files in Windows 7. To use it, extract the CAB file’s content (from the previously mentioned link) into a folder and run (as administrator) Install.cmd.