Windows X86 Assembly 101 see Iczelion's site. Very out of date as far as tools go, but the core Win32 kernel and API structure hasn't changed dramatically since Windows 4. (NT4 / Win9x)
Software Reverse Engineering 101, try OpenRCE, Woodman and Tuts4You.
Current and (reasonably) complete Win32 API can be looked up via MSDN of course. :wink:
