Hi,
this forum is intended for questions related to the Windows Research Kernel (WRK), which is why you may not get a satisfying answer here :(
However, there is a knowledge base maintained by MVPs about issues related to the HtmlHelp API. The URL is as follows:
Hopefully, you will find an answer there.
Best regards,
http://www.dcl.hpi.uni-potsdam.de/research/WRK