Fatal error C1189: #error : WINDOWS.H already included.

Question

Hi,
Can someone please explain why the following cpp file can get a compile error below?
C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\atlmfc\include\afxv_w32.h(16) : fatal error C1189: #error :  WINDOWS.H already included.  MFC apps must not #include <windows.h>
As you can see, there is only one include statement for afxwin.h.  I cannot think of any reason for this error.  Could you please help?  Thanks in advance.
JD
#include <afxwin.h>
//#include "resource.h"
//#include <atlbase.h>
//#include "CAData_i.h"
class CCADataModule : public CAtlDllModuleT< CCADataModule >
public :
 DECLARE_LIBID(LIBID_CADataLib)
CCADataModule _AtlModule;
// Used to determine whether the DLL can be unloaded by OLE
STDAPI DllCanUnloadNow(void)
    AFX_MANAGE_STATE(AfxGetStaticModuleState());
    return (AfxDllCanUnloadNow()==S_OK && _AtlModule.GetLockCount()==0) ? S_OK : S_FALSE;
// Returns a class factory to create an object of the requested type
STDAPI DllGetClassObject(REFCLSID rclsid, REFIID riid, LPVOID* ppv)
    return _AtlModule.DllGetClassObject(rclsid, riid, ppv);
// DllRegisterServer - Adds entries to the system registry
STDAPI DllRegisterServer(void)
    // registers object, typelib and all interfaces in typelib
    HRESULT hr = _AtlModule.DllRegisterServer();
 return hr;
// DllUnregisterServer - Removes entries from the system registry
STDAPI DllUnregisterServer(void)
 HRESULT hr = _AtlModule.DllUnregisterServer();
 return hr;

Answer 1

Hi Rajesh,
But, as you can see, I didn't include "stdafx.h" in the cpp file.  As I mentioned, there is only one include statement.  Another evidence is to add the 3 marco statements you recommended as below.  I get the same error.  The
middle macro statement is de-highlighted.  It means _windows_ is not defined.  So, somehow, in this case, afxwin itself causes this error.  I really cannot explain.  Any thought?  Thanks.
JD
#ifdef __windows__
#undef __windows__
#endif
#include <afxwin.h>
//#include "resource.h"
//#include <atlbase.h>
//#include "CAData_i.h"