Display HLP files with VistaTag(s): Misc Prog HowTo
Starting with the Windows Vista operating system release, the Windows Help program will not ship as a component of the Windows operating system. Also, third-party programs that include .hlp files are prohibited from redistributing the Windows Help program together with their products.
http://support.microsoft.com/?kbid=917607
Users who want to view 32-bit .hlp files must download the program from the Microsoft Download Center, and then install it on their computers.
To download WinHlp32.exe, visit the following Microsoft Web site: http://go.microsoft.com/fwlink/?LinkID=82148