Access to chm from tcl: winhelp
TJK: I'm no expert but the following items may be helpful to others. Please add your own comments, tools and links.
- A description of the file format can be found here 
- Abee Chm Maker is a program for making chm-files. It is free and can be downloaded from here . It has a simple and comprehensible interface that allow you to make CHM-files (with contents). I tried it on a simple problem, and it worked and seemed to be easy to use.
- An X-Windows viewer for .chm files can be downloaded from here . lexfiend 4 Dec 2005: This and several other *nix-based CHM viewers uses the "CHM lib" library , not to be confused with Matt Russotto's chmlib that can be found in his "CHM tools" package .
Comments on .chm files.DKF: "Isn't it HTML+postprocessing?"PT: "Yes. MS issue a HTML compiler. You can take a web site and turn it into a chm file quite easily. You have to dig around in MSDN to find the package to download though. It used to be on the Platform SDK disk."PT: It's called the MS HTML Help 1.4 SDK and you can download it from  and view the documentation there.
DAG: See also CHMvfs
With NT (?) and earlier, Microsoft's help format was .hlp, rather than .chm. Here  are products which run under Linux (among other platforms) and understand .hlp's (never-publicly-documented?) format.