Opening a CHM help file from a Delphi program

Modern versions of Delphi include the Vcl.HtmlHelpViewer unit which implements the wrapper for Windows HTMLHelp function API. Check Embarcadero's web-site to learn how to use it: http://docwiki.embarcadero.com/Libraries/en/Vcl.HtmlHelpViewer

Older versions of Delphi requires a dedicate unit. See: Older versions of Delphi