How can I display a Windows CHM help file from an applet?

You can use showDocument() to show any file that a browser to display. The key to displaying a CHM (.chm) file is to make sure the web server sets the appropriate content/MIME type. How to do this is specific to your web server.

As an alternative to using showDocument(), you can convert the CHM file to a JavaHelp file and use that API or just convert the data to an HTML file.