Win32 Programmer's Reference
Back in the day, long before Microsoft compiled the monstrosity now known as the MSDN Libraries, us Win32 developers leveraged the awing depths of "The Win32 Programmer's Reference". This document was distributed as a Microsoft Compiled Help file which served as a compressed, self-contained and fairly portable bible for those of us who were almost always disconnected (the internet was sporadic, slow and non-existent in these days). While old, it's still very useful to this day lower-level Windows developers.
Also, if you feel like being totally masochistic, I decompiled the entire help file and placed it here for online viewing: http://networkdls.com/Win32Ref/ (be warned, the index is 700K of HTML, so mobile viewing is a pain).