Parece que haverá uma mudança nos arquivos de help das novas versões do Windows (Vista / Longhorn). O formato .hlp parece que será descontinuado, sendo substituiído por novas tecnologias.

"Windows Help (WinHlp32.exe) is a help program that has been included with Microsoft Windows versions starting with the Microsoft Windows 3.1 operating system. The Windows Help program (WinHlp32.exe) is required to display 32-bit help content files that have the ".hlp" file name extension."
Continua: http://support.microsoft.com/kb/917607