KeyTools' best feature by far is its ability to extract source files from a .chm file and reconstruct a HTML Help Project (.hhp) file.
Note: RoboHelp Office also comes with a decompiler called the HTML Help Studio, however HTML Help Studio does not recreate the essential HTML Help project (.hhp) file, and therefore makes reconstruction of a project almost impossible.
The .hhp is a text file that contains project and file settings for a Microsoft HTML Help project. The project settings include the name of the help project, Help window configurations, the files used for the Table of Contents and Index, and the default Help topic, among other settings. In addition, all files used in the Help project are listed, such as HTML files, graphics, multimedia, context sensitive help files, plus add in files like JavaScript, XML, and RoboHelp browse sequences. When an HTML Help file is created, Microsoft's Compiler reads the project file and uses all the project references to produce a single Compressed HTML (CHM) file.
KeyTools can recreate most of the project file information stored in the CHM file including ALINK keyword associations. The resulting .hhp file can be opened using any HTML Help editor (RoboHelp, Doc-To-Help, ForeHelp, HTML Help Workshop, etc.) to convert it into a Help project. The only key files not recreated by KeyTools are the Map (.h) and Alias (.ali) files.
As a general rule, you should add these critical files (.hhp, .h, & .ali) into the BAGGAGE section of RoboHelp projects just before distribution so the files can be compiled into and to insure they always accompany the CHM file.