diff -ru gcc-4.5.1.orig/gcc/config/i386/mingw32.h gcc-4.5.1/gcc/config/i386/mingw32.h
--- gcc-4.5.1.orig/gcc/config/i386/mingw32.h	2010-04-27 22:14:19.000000000 +0200
+++ gcc-4.5.1/gcc/config/i386/mingw32.h	2010-09-01 16:56:49.000000000 +0200
@@ -66,7 +66,7 @@
 /* Override the standard choice of /usr/include as the default prefix
    to try when searching for header files.  */
 #undef STANDARD_INCLUDE_DIR
-#define STANDARD_INCLUDE_DIR "/mingw/include"
+#define STANDARD_INCLUDE_DIR "/include"
 #undef STANDARD_INCLUDE_COMPONENT
 #define STANDARD_INCLUDE_COMPONENT "MINGW"
 
diff -ru gcc-4.5.1.orig/gcc/config/i386/t-mingw32 gcc-4.5.1/gcc/config/i386/t-mingw32
--- gcc-4.5.1.orig/gcc/config/i386/t-mingw32	2008-09-04 10:25:25.000000000 +0200
+++ gcc-4.5.1/gcc/config/i386/t-mingw32	2010-09-01 16:26:49.000000000 +0200
@@ -1,5 +1,5 @@
 # Match SYSTEM_INCLUDE_DIR
-NATIVE_SYSTEM_HEADER_DIR = /mingw/include
+NATIVE_SYSTEM_HEADER_DIR = /include
 
 # MinGW-specific parts of LIB_SPEC
 SHLIB_LC = -lmingw32 -lmingwex -lmoldname -lmsvcrt -luser32 -lkernel32 -ladvapi32 -lshell32
diff -ru gcc-4.5.1.orig/libstdc++-v3/include/Makefile.am gcc-4.5.1/libstdc++-v3/include/Makefile.am
--- gcc-4.5.1.orig/libstdc++-v3/include/Makefile.am	2010-02-10 21:14:33.000000000 +0200
+++ gcc-4.5.1/libstdc++-v3/include/Makefile.am	2010-09-02 10:19:37.000000000 +0200
@@ -893,7 +893,7 @@
 	${pch1_output_builddir} ${pch2_output_builddir} ${pch3_output_builddir}
 pch_output_anchors = \
 	${pch1_output_anchor} ${pch2_output_anchor} ${pch3_output_anchor}
-PCHFLAGS=-x c++-header $(CXXFLAGS)
+PCHFLAGS=-nostdinc++ -x c++-header $(CXXFLAGS)
 if GLIBCXX_BUILD_PCH
 pch_build = ${pch_output}
 else
diff -ru gcc-4.5.1.orig/libstdc++-v3/include/Makefile.in gcc-4.5.1/libstdc++-v3/include/Makefile.in
--- gcc-4.5.1.orig/libstdc++-v3/include/Makefile.in	2010-04-02 20:18:06.000000000 +0200
+++ gcc-4.5.1/libstdc++-v3/include/Makefile.in	2010-09-02 10:26:05.000000000 +0200
@@ -1119,7 +1119,7 @@
 pch_output_anchors = \
 	${pch1_output_anchor} ${pch2_output_anchor} ${pch3_output_anchor}
 
-PCHFLAGS = -x c++-header $(CXXFLAGS)
+PCHFLAGS = -nostdinc++ -x c++-header $(CXXFLAGS)
 @GLIBCXX_BUILD_PCH_FALSE@pch_build = 
 @GLIBCXX_BUILD_PCH_TRUE@pch_build = ${pch_output}