diff --git a/ReactOS-generic.rbuild b/ReactOS-generic.rbuild
index 540bb9ab594..e0b3a72a4ff 100644
--- a/ReactOS-generic.rbuild
+++ b/ReactOS-generic.rbuild
@@ -64,8 +64,8 @@
 	<include root="intermediate">include/psdk</include>
 	<include>include/dxsdk</include>
 	<include root="intermediate">include/dxsdk</include>
-	<include>include/crt</include>
-	<include>include/crt/mingw32</include>
+	<!--<include>include/crt</include>-->
+	<!--<include>include/crt/mingw32</include>-->
 	<include>include/ddk</include>
 	<include>include/GL</include>
 	<include>include/ndk</include>
diff --git a/ReactOS-i386.rbuild b/ReactOS-i386.rbuild
index 8ddfbb57622..82ec6b20b9a 100644
--- a/ReactOS-i386.rbuild
+++ b/ReactOS-i386.rbuild
@@ -16,27 +16,41 @@
 	<property name="NTOSKRNL_SHARED" value="-file-alignment=0x1000 -section-alignment=0x1000 -shared"/>
 
 	<if property="OPTIMIZE" value="1">
+	<!--
 		<compilerflag>-Os</compilerflag>
 		<compilerflag>-ftracer</compilerflag>
 		<compilerflag>-momit-leaf-frame-pointer</compilerflag>
-	</if>
-	<if property="OPTIMIZE" value="2">
-		<compilerflag>-Os</compilerflag>
-	</if>
-	<if property="OPTIMIZE" value="3">
+	-->
 		<compilerflag>-O1</compilerflag>
 	</if>
-	<if property="OPTIMIZE" value="4">
+	<if property="OPTIMIZE" value="2">
+		<!--<compilerflag>-Os</compilerflag>-->
 		<compilerflag>-O2</compilerflag>
 	</if>
+	<if property="OPTIMIZE" value="3">
+		<!--<compilerflag>-O1</compilerflag>-->
+		<compilerflag>-Ox</compilerflag>
+		<compilerflag>-Os</compilerflag>
+	</if>
+	<if property="OPTIMIZE" value="4">
+		<!--<compilerflag>-O2</compilerflag>-->
+		<compilerflag>-Ox</compilerflag>
+		<compilerflag>-Os</compilerflag>
+	</if>
 	<if property="OPTIMIZE" value="5">
-		<compilerflag>-O3</compilerflag>
+		<!--<compilerflag>-O3</compilerflag>-->
+		<compilerflag>-Ox</compilerflag>
+		<compilerflag>-Os</compilerflag>
 	</if>
 
+	<!--
 	<compilerflag>-mpreferred-stack-boundary=2</compilerflag>
 	<compilerflag>-fno-strict-aliasing</compilerflag>
 	<compilerflag>-Wno-strict-aliasing</compilerflag>
 	<compilerflag>-Wpointer-arith</compilerflag>
+	-->
+	<compilerflag>-Oy-</compilerflag>
+	<compilerflag>-GS-</compilerflag>
 	<linkerflag>-disable-stdcall-fixup</linkerflag>
 
 </project>
diff --git a/dll/win32/aclui/guid.c b/dll/win32/aclui/guid.c
index 791f78ed154..3c661f5c8cf 100644
--- a/dll/win32/aclui/guid.c
+++ b/dll/win32/aclui/guid.c
@@ -19,8 +19,11 @@
 
 /* DO NOT USE THE PRECOMPILED HEADER FOR THIS FILE! */
 
-#include <initguid.h>
 #include <windows.h>
+
+#include <initguid.h>
+#include <objbase.h>
+
 #include <aclui.h>
 #include <objsel.h>
 
diff --git a/dll/win32/aclui/precomp.h b/dll/win32/aclui/precomp.h
index d300be0953b..48b4907c0c3 100644
--- a/dll/win32/aclui/precomp.h
+++ b/dll/win32/aclui/precomp.h
@@ -4,7 +4,7 @@
 #include <windows.h>
 #include <ndk/ntndk.h>
 #include <commctrl.h>
-#include <oleauto.h>
+#include <ole2.h>
 #include <objsel.h>
 #include <prsht.h>
 #include <aclui.h>
diff --git a/dll/win32/aclui/sidcache.c b/dll/win32/aclui/sidcache.c
index 5e8db066912..c5f49208947 100644
--- a/dll/win32/aclui/sidcache.c
+++ b/dll/win32/aclui/sidcache.c
@@ -178,7 +178,7 @@ OpenLSAPolicyHandle(IN LPWSTR SystemName,
     if (SystemName != NULL && SystemName[0] != L'\0')
     {
         LsaSystemName.Buffer = SystemName;
-        LsaSystemName.Length = wcslen(SystemName) * sizeof(WCHAR);
+        LsaSystemName.Length = (USHORT)(wcslen(SystemName) * sizeof(WCHAR)); /* FIXME: possible overflow */
         LsaSystemName.MaximumLength = LsaSystemName.Length + sizeof(WCHAR);
         psn = &LsaSystemName;
     }
diff --git a/drivers/bus/acpi/include/actypes.h b/drivers/bus/acpi/include/actypes.h
index c2cc1125ebc..cd406f7f5e5 100644
--- a/drivers/bus/acpi/include/actypes.h
+++ b/drivers/bus/acpi/include/actypes.h
@@ -193,11 +193,11 @@ typedef UINT64                          u64;
  */
 #ifdef _MSC_VER
 typedef ULONGLONG u64;
-typedef ULONG u32;
+//~ typedef ULONG u32;
 typedef USHORT u16;
 typedef UCHAR u8;
 typedef LONGLONG s64;
-typedef LONG s32;
+//~ typedef LONG s32;
 typedef SHORT s16;
 typedef CHAR s8;
 #endif
diff --git a/drivers/bus/acpi/include/platform/acenv.h b/drivers/bus/acpi/include/platform/acenv.h
index 9679222de8d..b73856be3bb 100644
--- a/drivers/bus/acpi/include/platform/acenv.h
+++ b/drivers/bus/acpi/include/platform/acenv.h
@@ -111,10 +111,10 @@
 #elif _AED_EFI
 #include "acefi.h"
 
-#elif WIN32
+#elif defined(WIN32)
 #include "acwin.h"
 
-#elif __FreeBSD__
+#elif defined(__FreeBSD__)
 #include "acfreebsd.h"
 
 #else
diff --git a/include/psdk/intrin.h b/include/psdk/intrin.h.bak
similarity index 100%
rename from include/psdk/intrin.h
rename to include/psdk/intrin.h.bak
diff --git a/lib/3rdparty/mingw/wcrt1.c b/lib/3rdparty/mingw/wcrt1.c
index df1cec8e3b2..59385ffb00c 100644
--- a/lib/3rdparty/mingw/wcrt1.c
+++ b/lib/3rdparty/mingw/wcrt1.c
@@ -42,7 +42,7 @@ extern int wmain (int, wchar_t **, wchar_t **);
 #define __UNKNOWN_APP    0
 #define __CONSOLE_APP    1
 #define __GUI_APP        2
-__MINGW_IMPORT void __set_app_type(int);
+_CRTIMP void __set_app_type(int);
 #endif /* __MSVCRT__ */
 
 /*  Global _fmode for this .exe, not the one in msvcrt.dll,
@@ -181,7 +181,7 @@ _gnu_exception_handler (EXCEPTION_POINTERS * exception_data)
 /*
  * The function mainCRTStartup is the entry point for all console programs.
  */
-static void  __attribute__((noreturn))
+static void  __declspec(noreturn)
 __mingw_wCRTStartup (void)
 {
   int nRet;
@@ -218,6 +218,7 @@ __mingw_wCRTStartup (void)
   _pei386_runtime_relocator ();
 #endif
 
+#if defined(__GNUC__)
 #if defined(__i386__)
   /* Align the stack to 16 bytes for the sake of SSE ops in main
      or in functions inlined into main.  */
@@ -230,6 +231,17 @@ __mingw_wCRTStartup (void)
   asm  __volatile__  ("li 0,15\n\tandc 1,1,0" : : : "r1");
 #else
 #error Unsupported architecture
+#endif
+#endif
+
+#if defined(_MSC_VER)
+#if defined(_M_IX86)
+  /* Align the stack to 16 bytes for the sake of SSE ops in main
+     or in functions inlined into main.  */
+  __asm and esp, 0FFFFFFF0h
+#else
+#error Unsupported architecture
+#endif
 #endif
 
   /*