I wanted to disable language extensions to be able to do some tests in my project. I found that I must set /Za compiler directive from http://msdn.microsoft.com/en-us/librar
The windows headers have never compiled with /Za.
There are other problems as well with /Za, that has caused Microsoft to stop testing their C++ standard library with that option. As told here:
http://permalink.gmane.org/gmane.comp.lib.boost.devel/212180
The recommendation is not to use it in "real" code.
Isolate your use of <windows.h>
into a source file(s) that you don't compile with /Za
and use the parameter on the other files.