When I try to compile my c++ project using Visual Studio 2010 in either Win32 or x64 mode I get the following error:
>C:\\Program Files (x86)\\Microsoft SDK
Another reason for the error (amongst many others that cropped up when changing the target build of a Win32 project to X64) was not having the C++ 64 bit compilers installed as noted at the top of this page.
Further to philipvr's comment on child headers, (in my case) an explicit include of winnt.h being unnecessary when windows.h was being used.