>Where do I find help on WIN32API for these parameters. I tried the API >section but could not find anything

Ah, but you didn't try the Microsoft Knowledge Base, did you? :-) Take a look at http://support.microsoft.com/support/kb/articles/Q190/8/78.ASP?LN=EN-US&SD=gn&FR=0. The article isn't specific to what you're wanting to do, but it gives you an example of how to use RegOpenKeyEx().