.HXK File Extension
File TypeMicrosoft Help 2 Index File
What is an HXK file?
File used by Microsoft Help 2.x projects; specifies information about how a help index is organized; often used for keyword, context-sensitive, and other help indexes defined in the .HXS help documentation bundle.
NOTE: Older versions of Visual Studio, including 2005 and 2008, used Microsoft Help 2.x as the standard help format. However, Visual Studio 2010 and later no longer support Microsoft Help 2.x.