diff --git a/checkin_notes b/checkin_notes
index ef2235c573..84946db503 100644
--- a/checkin_notes
+++ b/checkin_notes
@@ -8498,3 +8498,12 @@ Rom    7 Oct 2009
         ViewProjectsGrid.cpp, .h (deleted)
         ViewTransfersGrid.cpp, .h (deleted)
         ViewWorkGrid.cpp, .h (deleted)
+
+Bernd	7 Oct 2009
+    - lib: some changes to help building the WIN32 library with MinGW/gcc
+           enable by defining MINGW_WIN32 macro, nothing should change if
+	   this is not set
+    lib/
+	boinc_win.h
+	diagnostics.h
+	filesys.cpp
diff --git a/lib/boinc_win.h b/lib/boinc_win.h
index 51236efbdd..f4dcc606bb 100644
--- a/lib/boinc_win.h
+++ b/lib/boinc_win.h
@@ -96,7 +96,11 @@ typedef size_t socklen_t;
 
 #include <commctrl.h>
 #include <raserror.h>
+#if defined(MINGW_WIN32)
+#include <imagehlp.h>
+#else
 #include <dbghelp.h>
+#endif
 #include <tlhelp32.h>
 
 #include <io.h>
@@ -129,7 +133,9 @@ typedef LPCSTR PCTSTR, LPCTSTR, PCUTSTR, LPCUTSTR;
 // C headers
 #include <sys/stat.h>
 #include <sys/types.h>
+#if !defined(MINGW_WIN32)
 #include <fcntl.h>
+#endif
 #include <malloc.h>
 
 #if !defined(__MINGW32__) && !defined(__CYGWIN32__)
@@ -211,9 +217,11 @@ extern "C" {
 #endif
 void __cdecl _fpreset (void);
 void __cdecl fpreset (void);
+#ifndef MINGW_WIN32
 #define SetClassLongPtr SetClassLong
 #define GCLP_HICON GCL_HICON
 #define GCLP_HICONSM GCL_HICONSM
+#endif
 #ifdef __cplusplus
 }
 #endif
diff --git a/lib/diagnostics.h b/lib/diagnostics.h
index ab36e26257..f71801b2bb 100644
--- a/lib/diagnostics.h
+++ b/lib/diagnostics.h
@@ -114,7 +114,12 @@ extern int diagnostics_finish_unhandled_exception_monitor();
 #ifdef _WIN32
 extern UINT WINAPI diagnostics_unhandled_exception_monitor(LPVOID lpParameter);
 extern LONG CALLBACK boinc_catch_signal(EXCEPTION_POINTERS *ExceptionInfo);
+#ifndef MINGW_WIN32
 extern void boinc_catch_signal_invalid_parameter(const wchar_t* expression, const wchar_t* function, const wchar_t* file, unsigned int line, uintptr_t pReserved);
+#else
+extern void boinc_catch_signal_invalid_parameter(const wchar_t* expression, const wchar_t* function, const wchar_t* file, unsigned int line);
+#endif
+
 #else
 extern void boinc_catch_signal(int signal);
 extern void boinc_set_signal_handler(int sig, void(*handler)(int));
diff --git a/lib/filesys.cpp b/lib/filesys.cpp
index 2b270ee989..98ae0f719a 100644
--- a/lib/filesys.cpp
+++ b/lib/filesys.cpp
@@ -23,6 +23,10 @@
 #define getcwd  _getcwd
 #endif
 
+#if defined(MINGW_WIN32)
+#include <fcntl.h>
+#endif
+
 #if !defined(_WIN32) || defined(__CYGWIN32__)
 #include "config.h"
 #ifdef _USING_FCGI_