diff --git a/os/pl-mswchar.h b/os/pl-mswchar.h
deleted file mode 100644
index bac2c7d95..000000000
--- a/os/pl-mswchar.h
+++ /dev/null
@@ -1,39 +0,0 @@
-/*  $Id$
-
-    Part of SWI-Prolog
-
-    Author:        Jan Wielemaker
-    E-mail:        wielemak@science.uva.nl
-    WWW:           http://www.swi-prolog.org
-    Copyright (C): 1985-2005, University of Amsterdam
-
-    This library is free software; you can redistribute it and/or
-    modify it under the terms of the GNU Lesser General Public
-    License as published by the Free Software Foundation; either
-    version 2.1 of the License, or (at your option) any later version.
-
-    This library is distributed in the hope that it will be useful,
-    but WITHOUT ANY WARRANTY; without even the implied warranty of
-    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-    Lesser General Public License for more details.
-
-    You should have received a copy of the GNU Lesser General Public
-    License along with this library; if not, write to the Free Software
-    Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
-*/
-
-#include <wchar.h>
-
-/* - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -
-See pl-mswchar.cpp for  the  motivation  for   this  nonsense.  Used  in
-pl-fli.c and pl-text.c.
-- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - */
-
-#if defined(__WINDOWS__) && !defined(__MINGW32__)
-
-#define wcrtomb(s, wc, ps)	ms_wcrtomb(s, wc, ps)
-#define mbrtowc(pwc, s, n, ps)	ms_mbrtowc(pwc, s, n, ps)
-
-extern size_t ms_wcrtomb(char *s, wchar_t wc, mbstate_t *ps);
-extern size_t ms_mbrtowc(wchar_t *pwc, const char *s, size_t n, mbstate_t *ps);
-#endif
diff --git a/os/pl-nt.c b/os/pl-nt.c
index 957a40c5b..fcb6d9a7d 100755
--- a/os/pl-nt.c
+++ b/os/pl-nt.c
@@ -47,12 +47,24 @@
 #endif
 
 #include "pl-incl.h"
+#ifdef __YAP_PROLOG__
+#include "pl-utf8.h"
+#else
 #include "os/pl-utf8.h"
+#endif
 #include <process.h>
+#ifdef __YAP_PROLOG__
+#include "pl-ctype.h"
+#else
 #include "os/pl-ctype.h"
+#endif
 #include <stdio.h>
 #include <stdarg.h>
+#ifdef __YAP_PROLOG__
+#include "SWI-Stream.h"
+#else
 #include "os/SWI-Stream.h"
+#endif
 #include <process.h>
 #include <winbase.h>
 #ifdef HAVE_CRTDBG_H
@@ -1108,8 +1120,10 @@ BeginPredDefs(win)
   PRED_DEF("win_shell", 3, win_shell3, 0)
   PRED_DEF("win_registry_get_value", 3, win_registry_get_value, 0)
   PRED_DEF("win_folder", 2, win_folder, PL_FA_NONDETERMINISTIC)
+#ifdef EMULATE_DLOPEN
   PRED_DEF("win_add_dll_directory", 2, win_add_dll_directory, 0)
   PRED_DEF("win_remove_dll_directory", 1, win_remove_dll_directory, 0)
+#endif
 EndPredDefs
 
 #endif /*__WINDOWS__*/