diff --git a/win/rfb_win32/OSVersion.cxx b/win/rfb_win32/OSVersion.cxx
new file mode 100644
index 0000000..3d74c95
--- /dev/null
+++ b/win/rfb_win32/OSVersion.cxx
@@ -0,0 +1,47 @@
+/* Copyright (C) 2002-2005 RealVNC Ltd.  All Rights Reserved.
+ * 
+ * This is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation; either version 2 of the License, or
+ * (at your option) any later version.
+ * 
+ * This software 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 General Public License for more details.
+ * 
+ * You should have received a copy of the GNU General Public License
+ * along with this software; if not, write to the Free Software
+ * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307,
+ * USA.
+ */
+
+// -=- OSVersion.cxx
+
+#include <rfb_win32/OSVersion.h>
+#include <rdr/Exception.h>
+#include <tchar.h>
+
+using namespace rfb;
+using namespace win32;
+
+
+OSVersionInfo::OSVersionInfo() {
+  // Get OS Version Info
+  ZeroMemory(static_cast<OSVERSIONINFO*>(this), sizeof(this));
+  dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
+  if (!GetVersionEx(this))
+    throw rdr::SystemException("unable to get system version info", GetLastError());
+
+  // Set the special extra flags
+  isPlatformNT = dwPlatformId == VER_PLATFORM_WIN32_NT;
+  isPlatformWindows = dwPlatformId == VER_PLATFORM_WIN32_WINDOWS;
+
+  cannotSwitchDesktop = isPlatformNT && (dwMajorVersion==4) &&
+    ((_tcscmp(szCSDVersion, _T("")) == 0) ||
+     (_tcscmp(szCSDVersion, _T("Service Pack 1")) == 0) ||
+     (_tcscmp(szCSDVersion, _T("Service Pack 2")) == 0));
+
+}
+
+OSVersionInfo rfb::win32::osVersion;