If your help is going to be installed on a network you should not use either CHM or HLP. WinHelp is more than a bit of a dog and it will NOT work in Vista; all you will get will be an error message. Microsoft has promised a "reader" for WinHelp for Vista, but this has not materialized yet and it is very likely that it will be only a reader, not supporting any kinds of calls to the help from your application.So the question is this, for new electronic documentation, that will most probably be installed on a network, which format would you run with;
The only real option for help on networks at the moment is Browser-based Help. This is robust and completely cross-platform -- it will work on all browsers on Windows, Mac and Linux, even on old browsers and browsers with JavaScript turned off. It elminates all the problems you have with CHMs on networks and you can also create context calls to Browser Help using normal URLs, with the syntax:
index.html?topicid.htm#anchorid
Where index.html is the index file of your compiled help, topicid is the ID of the topic you want to access in all lower case letters and anchorid is the name of an optional anchor (jump target) in a topic.