Creating Dual-Mode Context-Sensitive Help
http://www.componentone.com/d2hhelp/158.dual.modecontext.sensitivehelp.asp

ComponentOne
1999

Abstract:

Want to provide your users with state-of-the art HTML Help but don't want to force them to install Internet Explorer (which is required to run compiled HTML Help files)? In this article we show you how to create context-sensitive Help that displays a topic from a .CHM file if IE is installed on the user's system, and displays the equivalent topic from a .HLP file if IE isn't installed.