The Microsoft Win32 Programmer's Reference in CHM Format can be downloaded from here: http://laurencejackson.com/win32/index.html
This help file is an excellent source of documentation for many aspects of the Win32 API.
NOTE: To get the file to load correctly it will need to be unblocked using the option found using the Properties menu:
Once the file is unblocked it works perfectly with the Zeus Quick Help searching feature:
Cheers Jussi