diff -Naur mlton-r6658.patched/runtime/platform/mingw.h mlton-r6658/runtime/platform/mingw.h
--- mlton-r6658.patched/runtime/platform/mingw.h	2008-06-16 17:39:27.000000000 +0200
+++ mlton-r6658/runtime/platform/mingw.h	2008-06-18 18:42:49.000000000 +0200
@@ -265,7 +288,7 @@
         char machine[20];
         char nodename[256];
         char release[20];
-        char sysname[20];
+        char sysname[30];
         char version[20];
 };
 
--- mlton-r6658.orig/runtime/platform/mingw.c	2008-06-16 16:02:50.000000000 +0200
+++ mlton-r6658/runtime/platform/mingw.c	2008-06-16 19:26:51.000000000 +0200
@@ -520,25 +520,72 @@
 }
 
 static void setSysname (struct utsname *buf) {
-        OSVERSIONINFO osv;
+        OSVERSIONINFOEX osv;
         const char* os = "??";
 
+#ifndef _WIN64
+	/* Call GetNativeSystemInfo if supported or GetSystemInfo otherwise. */
+	SYSTEM_INFO si;
+	void (WINAPI *pGNSI)(LPSYSTEM_INFO);
+	pGNSI = (PVOID) GetProcAddress(GetModuleHandle(TEXT("kernel32.dll")),
+				       "GetNativeSystemInfo");
+	if (NULL != pGNSI)
+	  pGNSI(&si);
+	else
+	  GetSystemInfo(&si);
+#endif
+
         osv.dwOSVersionInfoSize = sizeof (osv);
-        GetVersionEx (&osv);
+	/* Try to get extended information in order to be able to match the O.S. more
+	   precisely using osv.wProductType */
+        if (! GetVersionEx ((OSVERSIONINFO *) &osv)) {
+	  ZeroMemory(&osv, sizeof(OSVERSIONINFOEX));
+	  osv.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
+	  GetVersionEx((OSVERSIONINFO *) &osv);
+	}
         switch (osv.dwPlatformId) {
         case VER_PLATFORM_WIN32_NT:
+#ifdef _WIN64
+	        if (osv.dwMinorVersion == 0) {
+		  if (osv.dwMajorVersion <= 6) {
+		    if (osv.wProductType == VER_NT_WORKSTATION)
+		                                          os = "Vista_64";
+		    else
+		                                          os = "2008_64";
+		  } else                                  os = "NTx_64";
+		} else if (osv.dwMinorVersion <= 2)       os = "XP_64";
+		else                                      os = "NTx_64";
+#else
                 if (osv.dwMinorVersion == 0) {
-                        if (osv.dwMajorVersion <= 4)    os = "NT";
-                        else                            os = "2000";
-                } else if (osv.dwMinorVersion <= 1)     os = "XP";
-                else if (osv.dwMinorVersion <= 2)       os = "2003";
-                else                                    os = "NTx";
+                        if (osv.dwMajorVersion <= 4)      os = "NT";
+                        else if (osv.dwMajorVersion <= 5) os = "2000";
+			else {
+			  if (osv.wProductType == VER_NT_WORKSTATION) {
+			    if (si.wProcessorArchitecture == PROCESSOR_ARCHITECTURE_AMD64)
+			                                  os = "Vista_WOW64";
+			    else
+			                                  os = "Vista";
+			  } else {
+			    if (si.wProcessorArchitecture == PROCESSOR_ARCHITECTURE_AMD64)
+			                                  os = "2008";
+			    else
+			                                  os = "2008_WOW64";
+			  }
+			}
+                } else if (osv.dwMinorVersion <= 1)       os = "XP";
+		else if (osv.dwMinorVersion <= 2) {
+		  if (si.wProcessorArchitecture == PROCESSOR_ARCHITECTURE_AMD64)
+		                                          os = "XP_WOW64";
+		  else
+		                                          os = "2003";
+                } else                                    os = "NTx";
+#endif
                 break;
         case VER_PLATFORM_WIN32_WINDOWS:
-                if (osv.dwMinorVersion == 0)            os = "95";
-                else if (osv.dwMinorVersion < 90)       os = "98";
-                else if (osv.dwMinorVersion == 90)      os = "Me";
-                else                                    os = "9X";
+                if (osv.dwMinorVersion == 0)              os = "95";
+                else if (osv.dwMinorVersion < 90)         os = "98";
+                else if (osv.dwMinorVersion == 90)        os = "Me";
+                else                                      os = "9X";
                 break;
         case VER_PLATFORM_WIN32s:
                 os = "31"; /* aka DOS + Windows 3.1 */