Use #include "foo.h" for including Windows headers in dlls/, use
#include <bar.h> for including Windows headers in include/.

diff --git a/include/msxml.idl b/include/msxml.idl
index 328d8aa..5f20f98 100644
--- a/include/msxml.idl
+++ b/include/msxml.idl
@@ -17,7 +17,7 @@
  * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  */
 
-#include "msxmldid.h"
+#include <msxmldid.h>
 
 import "unknwn.idl";
 import "wtypes.idl";