I find this error when compiling a class which includes some .h files, and many of them surely includes <windows.h>

The error is:
c:\archivos de programa\microsoft visual studio\vc98\mfc\include\afxv_w32.h(14) : fatal error C1189: #error : WINDOWS.H already included. MFC apps must not #include <windows.h>

The problem is that only when including a class made by me, which includes <afxwin.h> or <afxmt.h>, the error appears. No problem with other included .h files which include <windows.h>