diff --git a/Makefile b/Makefile
index 36b7909648..ae4e9b144c 100644
--- a/Makefile
+++ b/Makefile
@@ -385,7 +385,7 @@ win32-racket-then-cs:
 	$(MAKE) win32-base PKGS="" $(WIN32_CS_COPY_ARGS_EXCEPT_PKGS_SUT) WIN32_BUILD_LEVEL="$(WIN32_BUILD_LEVEL)"
 	$(MAKE) win32-just-cs RACKET=$(WIN32_PLAIN_RACKET) $(WIN32_CS_COPY_ARGS_BOOT)
 
-CSBUILD_ARGUMENTS = --scheme-dir "$(SCHEME_SRC)" \
+CSBUILD_ARGUMENTS = --scheme-dir "$(SCHEME_SRC)" --pull \
                     --racketcs-suffix "$(RACKETCS_SUFFIX)" \
                     --boot-mode "$(SETUP_BOOT_MODE)" \
                     --extra-repos-base "$(EXTRA_REPOS_BASE)" \
diff --git a/racket/src/cs/Makefile b/racket/src/cs/Makefile
index 84bc6f6a29..f06dab8fa9 100644
--- a/racket/src/cs/Makefile
+++ b/racket/src/cs/Makefile
@@ -19,7 +19,7 @@ RUMBLE_UNSAFE_COMP = --unsafe
 COMPILE_FILE = $(SCHEME) --script compile-file.ss $(UNSAFE_COMP) $(COMPRESS_COMP) $(DEBUG_COMP) --dest "$(BUILDDIR)"
 COMPILE_FILE_DEPS = compile-file.ss include.ss place-register.ss 
 
-RACKET_SETUP_ARGS = ../../bin/racket ../collects ../etc 0 true false
+RACKET_SETUP_ARGS = ../../bin/racket ../collects ../etc 0 true false 0 ""
 
 PRIMITIVES_TABLES = primitive/kernel.ss primitive/unsafe.ss primitive/flfxnum.ss \
                     primitive/paramz.ss primitive/extfl.ss primitive/network.ss \
diff --git a/racket/src/cs/c/boot.c b/racket/src/cs/c/boot.c
index 37d768e279..9cfcc46722 100644
--- a/racket/src/cs/c/boot.c
+++ b/racket/src/cs/c/boot.c
@@ -88,7 +88,8 @@ void racket_boot(int argc, char **argv, char *self,
 		 char *boot_exe, long segment_offset,
                  char *coldir, char *configdir,
                  int pos1, int pos2, int pos3,
-                 int cs_compiled_subdir, int is_gui)
+                 int cs_compiled_subdir, int is_gui,
+		 int wm_is_gracket, const char *gracket_guid)
 /* exe argument already stripped from argv */
 {
 #if !defined(RACKET_USE_FRAMEWORK) || !defined(RACKET_AS_BOOT)
@@ -134,11 +135,14 @@ void racket_boot(int argc, char **argv, char *self,
   {
     ptr l = Snil;
     int i;
-    char segment_offset_s[32];
+    char segment_offset_s[32], wm_is_gracket_s[32];
 
     for (i = argc; i--; ) {
       l = Scons(Sbytevector(argv[i]), l);
     }
+    l = Scons(Sbytevector(gracket_guid), l);
+    sprintf(wm_is_gracket_s, "%ld", wm_is_gracket);
+    l = Scons(Sbytevector(wm_is_gracket_s), l);
     l = Scons(Sbytevector(is_gui ? "true" : "false"), l);
     l = Scons(Sbytevector(cs_compiled_subdir ? "true" : "false"), l);
     sprintf(segment_offset_s, "%ld", segment_offset);
diff --git a/racket/src/cs/c/boot.h b/racket/src/cs/c/boot.h
index e7d322a1c7..d768704fa0 100644
--- a/racket/src/cs/c/boot.h
+++ b/racket/src/cs/c/boot.h
@@ -2,10 +2,12 @@ BOOT_EXTERN void racket_boot(int argc, char **argv, char *self,
 			     char *boot_exe, long segment_offset,
 			     char *coldir, char *configdir,
 			     int pos1, int pos2, int pos3,
-			     int cs_compiled_subdir, int is_gui);
+			     int cs_compiled_subdir, int is_gui,
+			     int wm_is_gracket, const char *gracket_guid);
 
 typedef void (*racket_boot_t)(int argc, char **argv, char *self,
 			      char* boot_exe, long segment_offset,
 			      char *coldir, char *configdir,
 			      int pos1, int pos2, int pos3,
-			      int cs_compiled_subdir, int is_gui);
+			      int cs_compiled_subdir, int is_gui,
+			      int wm_is_gracket, const char *gracket_guid);
diff --git a/racket/src/cs/c/grmain.c b/racket/src/cs/c/grmain.c
index 4edd8d172a..6b88833bec 100644
--- a/racket/src/cs/c/grmain.c
+++ b/racket/src/cs/c/grmain.c
@@ -9,6 +9,17 @@ static void pre_filter_cmdline_arguments(int *argc, char ***argv);
 # ifndef INITIAL_COLLECTS_DIRECTORY
 #  define INITIAL_COLLECTS_DIRECTORY "../collects"
 # endif
+# ifndef INITIAL_CONFIG_DIRECTORY
+#  define INITIAL_CONFIG_DIRECTORY "../etc"
+# endif
+
+/* Hack: overwrite "y" with "n" in binary to disable checking for another
+   instance of the same app. */
+char *check_for_another = "yes, please check for another";
+
+# include <Windows.h>
+# include "../start/win_single.inc"
+# define CHECK_SINGLE_INSTANCE
 #endif
 
 #include "main.c"
diff --git a/racket/src/cs/c/main.c b/racket/src/cs/c/main.c
index e55d470870..df480da448 100644
--- a/racket/src/cs/c/main.c
+++ b/racket/src/cs/c/main.c
@@ -125,9 +125,8 @@ static long find_boot_section(char *me)
 }
 #endif
 
-
 #ifdef WIN32
-static char *path_to_utf8(wchar_t *p)
+static char *string_to_utf8(wchar_t *p)
 {
   char *r;
   int len;
@@ -141,7 +140,7 @@ static char *path_to_utf8(wchar_t *p)
 
 static char *get_self_path()
 {
-  return path_to_utf8(get_self_executable_path());
+  return string_to_utf8(get_self_executable_path());
 }
 
 static int scheme_utf8_encode(unsigned int *path, int zero_offset, int len,
@@ -149,6 +148,8 @@ static int scheme_utf8_encode(unsigned int *path, int zero_offset, int len,
 {
   return WideCharToMultiByte(CP_UTF8, 0, (wchar_t *)path, len, dest, dest_len, NULL, NULL);
 }
+
+# include "../start/parse_cmdl.inc"
 #endif
 
 #ifdef NO_GET_SEGMENT_OFFSET
@@ -162,7 +163,9 @@ static long get_segment_offset()
 # define do_pre_filter_cmdline_arguments(argc, argv) /* empty */
 #endif
 
-int main(int argc, char **argv)
+static int bytes_main(int argc, char **argv,
+		      /* for Windows GUI mode */
+		      int wm_is_gracket, const char *gracket_guid)
 {
   char *self, *boot_exe, *prog = argv[0], *sprog = NULL;
   int pos1, pos2, pos3;
@@ -176,8 +179,10 @@ int main(int argc, char **argv)
   
   do_pre_filter_cmdline_arguments(&argc, &argv);
 
-  argc--;
-  argv++;
+  if (argc) {
+    argc--;
+    argv++;
+  }
 
   extract_built_in_arguments(&prog, &sprog, &argc, &argv);
   segment_offset = get_segment_offset();
@@ -187,7 +192,7 @@ int main(int argc, char **argv)
 #ifdef WIN32
 # define racket_boot racket_boot_p
   dll_path = load_delayed_dll_x(NULL, "libracketcsxxxxxxx.dll", &dll);
-  boot_exe = path_to_utf8(dll_path);
+  boot_exe = string_to_utf8(dll_path);
   racket_boot_p = (racket_boot_t)GetProcAddress(dll, "racket_boot");
 #else
   boot_exe = self;
@@ -213,7 +218,44 @@ int main(int argc, char **argv)
 	      boot_exe, segment_offset,
               extract_coldir(), extract_configdir(),
               pos1, pos2, pos3,
-              CS_COMPILED_SUBDIR, RACKET_IS_GUI);
+              CS_COMPILED_SUBDIR, RACKET_IS_GUI,
+	      wm_is_gracket, gracket_guid);
   
   return 0;
 }
+
+#if defined(WIN32) && defined(CHECK_SINGLE_INSTANCE)
+int APIENTRY WinMain(HINSTANCE hInstance, HINSTANCE hPrevInstance, LPSTR ignored, int nCmdShow)
+{
+  int argc;
+  char **argv;
+  char *normalized_path;
+  int wm = 0;
+  const char *guid = "";
+
+  argv = cmdline_to_argv(&argc, &normalized_path);
+
+  if (CheckSingleInstance(normalized_path, argv))
+    return 0;
+  wm = wm_is_gracket;
+  guid = GRACKET_GUID;
+
+  return bytes_main(argc, argv, wm, guid);
+}
+#elif defined(WIN32)
+int wmain(int argc, wchar_t **wargv)
+{
+  int i;
+  char **argv = malloc(argc * sizeof(char*));
+
+  for (i = 0; i < argc; i++) {
+    argv[i] = string_to_utf8(wargv[i]);
+  }
+
+  return bytes_main(argc, argv, 0, "");
+}
+#else
+int main(int argc, char **argv) {
+  return bytes_main(argc, argv, 0, "");
+}
+#endif
diff --git a/racket/src/cs/main.sps b/racket/src/cs/main.sps
index 6bc5520a67..bf053ce2ac 100644
--- a/racket/src/cs/main.sps
+++ b/racket/src/cs/main.sps
@@ -55,9 +55,14 @@
                           s))
           the-command-line-arguments/maybe-bytes))
 
+   (define builtin-argc 8)
    (seq
-    (unless (>= (length the-command-line-arguments) 6)
-      (error 'racket "expected `self`, `collects`, and `libs` paths plus `segment-offset`, `cs-compiled-subdir?`, and `is-gui?` to start"))
+    (unless (>= (length the-command-line-arguments) builtin-argc)
+      (error 'racket (string-append
+		      "expected `self`, `collects`, and `libs` paths"
+		      " plus `segment-offset`, `cs-compiled-subdir?`, `is-gui?`,"
+		      " `wm-is-gracket`, and `gracket-guid`"
+		      " to start")))
     (set-exec-file! (path->complete-path (car the-command-line-arguments))))
    (define init-collects-dir (let ([s (cadr the-command-line-arguments)])
                                (if (equal? s "") 'disable (string->path s))))
@@ -66,10 +71,18 @@
    (define segment-offset (#%string->number (list-ref the-command-line-arguments 3)))
    (define cs-compiled-subdir? (string=? "true" (list-ref the-command-line-arguments 4)))
    (define gracket? (string=? "true" (list-ref the-command-line-arguments 5)))
+   (define wm-is-gracket (string->number (list-ref the-command-line-arguments 6)))
+   (define gracket-guid (list-ref the-command-line-arguments 7))
 
    (seq
     (when (foreign-entry? "racket_exit")
-      (#%exit-handler (foreign-procedure "racket_exit" (int) void))))
+      (#%exit-handler (foreign-procedure "racket_exit" (int) void)))
+
+    ;; For Windows:
+    (unsafe-register-process-global (string->bytes/utf-8 "PLT_WM_IS_GRACKET")
+				    (ptr-add #f wm-is-gracket))
+    (unsafe-register-process-global (string->bytes/utf-8 "PLT_GRACKET_GUID")
+				    (bytes-append (string->bytes/utf-8 gracket-guid) #vu8(0))))
 
    (define compiled-file-paths
      (list (string->path (cond
@@ -227,7 +240,7 @@
    (define remaining-command-line-arguments '#())
 
    (seq
-    (let flags-loop ([args (list-tail the-command-line-arguments 6)]
+    (let flags-loop ([args (list-tail the-command-line-arguments builtin-argc)]
                      [saw (hasheq)])
       ;; An element of `args` can become `(cons _arg _within-arg)`
       ;; due to splitting multiple flags with a single "-"
diff --git a/racket/src/gracket/grmain.c b/racket/src/gracket/grmain.c
index 7ee42fc938..2e4353223f 100644
--- a/racket/src/gracket/grmain.c
+++ b/racket/src/gracket/grmain.c
@@ -412,175 +412,7 @@ static void MrEdExit(int v)
 START_XFORM_SKIP;
 # endif
 
-/* ---------------------------------------- */
-/*        single-instance detection         */
-/* ---------------------------------------- */
-
-static char *CreateUniqueName()
-{
-  char desktop[MAX_PATH], session[32], *together;
-  int dlen, slen;
-
-  {
-    // Name should be desktop unique, so add current desktop name
-    HDESK hDesk;
-    ULONG cchDesk = MAX_PATH - 1;
-
-    hDesk = GetThreadDesktop(GetCurrentThreadId());
-    
-    if (!GetUserObjectInformation( hDesk, UOI_NAME, desktop, cchDesk, &cchDesk))
-      desktop[0] = 0;
-    else
-      desktop[MAX_PATH - 1]  = 0;
-  }
-
-  {
-    // Name should be session unique, so add current session id
-    HANDLE hToken = NULL;
-    // Try to open the token (fails on Win9x) and check necessary buffer size
-    if (OpenProcessToken(GetCurrentProcess(), TOKEN_QUERY, &hToken)) {
-      DWORD cbBytes = 0;
-      
-      if(!GetTokenInformation( hToken, TokenStatistics, NULL, cbBytes, &cbBytes ) 
-	 && GetLastError() == ERROR_INSUFFICIENT_BUFFER) {
-	  PTOKEN_STATISTICS pTS;
-
-	  pTS = (PTOKEN_STATISTICS)malloc(cbBytes);
-	  
-	  if(GetTokenInformation(hToken, TokenStatistics, (LPVOID)pTS, cbBytes, &cbBytes)) {
-	    sprintf(session, "-%08x%08x-",
-		    pTS->AuthenticationId.HighPart, 
-		    pTS->AuthenticationId.LowPart);
-	  } else
-	    session[0] = 0;
-	  free(pTS);
-      } else {
-	session[0] = 0;
-      }
-    } else
-      session[0] = 0;
-  }
-
-  dlen = strlen(desktop);
-  slen =  strlen(session);
-  together = (char *)malloc(slen + dlen + 1);
-  memcpy(together, desktop, dlen);
-  memcpy(together + dlen, session, slen);
-  together[dlen + slen] = 0;
-  
-  return together;
-}
-
-#define GRACKET_GUID "B2261834-D535-44dd-8511-A26FC8F97DD0"
-
-static int wm_is_gracket;
-
-static BOOL CALLBACK CheckWindow(HWND wnd, LPARAM param)
-{
-  int i, len, gl;
-  DWORD w;
-  char **argv, *v;
-  COPYDATASTRUCT cd;
-  DWORD_PTR result;
-  LRESULT ok;
-
-  ok = SendMessageTimeout(wnd, wm_is_gracket,
-			  0, 0, 
-			  SMTO_BLOCK |
-			  SMTO_ABORTIFHUNG,
-			  200,
-			  &result);
-
-  printf("try %p result %d\n", wnd, result);
-
-  if (ok == 0)
-    return TRUE; /* ignore and continue */
-  if ((intptr_t)result == 79) {
-    /* found it */
-  } else
-    return TRUE; /* continue search */
-
-  /* wnd is owned by another instance of this application */
-
-  SetForegroundWindow(wnd);
-  if (IsIconic(wnd)) 
-    ShowWindow(wnd, SW_RESTORE);
-
-  argv = (char **)param;
-  
-  len = gl = strlen(GRACKET_GUID);
-  len += 4 + sizeof(DWORD);
-  for (i = 1; argv[i]; i++) {
-    len += sizeof(DWORD) + strlen(argv[i]);
-  }
-  w = i - 1;
-
-  v = (char *)malloc(len);
-  memcpy(v, GRACKET_GUID, gl);
-  memcpy(v + gl, "OPEN", 4);
-  memcpy(v + gl + 4, &w, sizeof(DWORD));
-  len = gl + 4 + sizeof(DWORD);
-  for (i = 1; argv[i]; i++) {
-    w = strlen(argv[i]);
-    memcpy(v + len, &w, sizeof(DWORD));
-    len += sizeof(DWORD);
-    memcpy(v + len, argv[i], w);
-    len += w;
-  }
-
-  cd.dwData = 79;
-  cd.cbData = len;
-  cd.lpData = v;
-
-  SendMessage(wnd, WM_COPYDATA, (WPARAM)wnd, (LPARAM)&cd);
-
-  free(v);
-
-  return FALSE;
-}
-
-static int CheckSingleInstance(char *normalized_path, char **argv)
-{
-  /* Check for an existing instance: */
-  if (check_for_another[0] != 'n') {
-    int alreadyrunning;
-    HANDLE mutex;
-    int j, l, i;
-    char *a, *b;
-
-    /* This mutex creation synchronizes multiple instances of
-       the application that may have been started. */
-    j = strlen(normalized_path);
-    
-    b = CreateUniqueName();
-    l = strlen(b);
-    a = (char *)malloc(j + l + 50);
-    memcpy(a, normalized_path, j);
-    for (i = 0; i < j; i++) {
-      /* backslashes are not allowed in mutex names */
-      if (a[i] == '\\') a[i] = '/';
-    }
-    memcpy(a + j, b, l);
-    memcpy(a + j + l, "GRacket-" GRACKET_GUID, strlen(GRACKET_GUID) + 9);
-    mutex = CreateMutex(NULL, FALSE, a);
-    alreadyrunning = (GetLastError() == ERROR_ALREADY_EXISTS || 
-		      GetLastError() == ERROR_ACCESS_DENIED);
-    /* The call fails with ERROR_ACCESS_DENIED if the Mutex was 
-       created in a different users session because of passing
-       NULL for the SECURITY_ATTRIBUTES on Mutex creation. */
-    wm_is_gracket = RegisterWindowMessage(a);
-    free(a);
-
-    if (alreadyrunning) {
-      /* If another instance has been started, try to find it. */
-      if (!EnumWindows((WNDENUMPROC)CheckWindow, (LPARAM)argv)) {
-	return 1;
-      }
-    }
-  }
-
-  return 0;
-}
+# include "../start/win_single.inc"
 
 static void pre_filter_cmdline_arguments(int *argc, char ***argv)
 {
diff --git a/racket/src/mzcom/mzcom.cxx b/racket/src/mzcom/mzcom.cxx
index 86eb7d2dec..c8f5398378 100644
--- a/racket/src/mzcom/mzcom.cxx
+++ b/racket/src/mzcom/mzcom.cxx
@@ -123,7 +123,7 @@ int IsFlag(LPCTSTR cmd, LPCTSTR flag)
 
 #define ASSUME_ASCII_COMMAND_LINE
 #define GC_CAN_IGNORE
-#include "../racket/parse_cmdl.inc"
+#include "../start/parse_cmdl.inc"
 
 /////////////////////////////////////////////////////////////////////////////
 //
diff --git a/racket/src/racket/Makefile.in b/racket/src/racket/Makefile.in
index b8df9fb74d..4d5c4a0aa3 100644
--- a/racket/src/racket/Makefile.in
+++ b/racket/src/racket/Makefile.in
@@ -272,8 +272,8 @@ DEF_CONFIG_DIR = -DINITIAL_CONFIG_DIRECTORY='"'"`cd $(srcdir)/../..; @PWD@`/etc"
 DEF_C_DIRS = $(DEF_COLLECTS_DIR) $(DEF_CONFIG_DIR)
 
 MAIN_HEADER_DEPS = $(srcdir)/include/scheme.h $(srcdir)/include/schthread.h $(srcdir)/sconfig.h \
-                   $(srcdir)/src/stypes.h $(srcdir)/cmdline.inc $(srcdir)/parse_cmdl.inc \
-	           $(srcdir)/../start/config.inc $(srcdir)/../start/delayed.inc $(srcdir)/parse_cmdl.inc \
+                   $(srcdir)/src/stypes.h $(srcdir)/cmdline.inc $(srcdir)/../start/parse_cmdl.inc \
+	           $(srcdir)/../start/config.inc $(srcdir)/../start/delayed.inc \
 	           $(srcdir)/../start/embedded_dll.inc
 
 main.@LTO@: $(srcdir)/main.c $(MAIN_HEADER_DEPS)
diff --git a/racket/src/racket/main.c b/racket/src/racket/main.c
index 0be8e3f8a5..6733126739 100644
--- a/racket/src/racket/main.c
+++ b/racket/src/racket/main.c
@@ -306,7 +306,7 @@ START_XFORM_SKIP;
 # endif
 
 #if defined(__MINGW32__) || defined(WINMAIN_ALREADY)
-# include "parse_cmdl.inc"
+# include "../start/parse_cmdl.inc"
 #endif
 
 #ifdef DOS_FILE_SYSTEM
diff --git a/racket/src/start/delayed.inc b/racket/src/start/delayed.inc
index 4710b30130..6dd5a8306b 100644
--- a/racket/src/start/delayed.inc
+++ b/racket/src/start/delayed.inc
@@ -86,6 +86,9 @@ static wchar_t *load_delayed_dll_x(HINSTANCE me, const char *lib, HMODULE *_load
       return t;
     }
   }
+
+  /* Should not get here */
+  return NULL;
 }
 
 static void load_delayed_dll(HINSTANCE me, const char *lib)
diff --git a/racket/src/start/embedded_dll.inc b/racket/src/start/embedded_dll.inc
index 30758eca08..579285f58c 100644
--- a/racket/src/start/embedded_dll.inc
+++ b/racket/src/start/embedded_dll.inc
@@ -38,7 +38,7 @@ static void parse_embedded_dlls()
 {
   long rsrc_pos;
 
-  rsrc_pos = find_resource_offset(258);
+  rsrc_pos = find_resource_offset(get_self_executable_path(), 258);
   if (rsrc_pos) {
     HANDLE fd = open_self();
     
diff --git a/racket/src/racket/parse_cmdl.inc b/racket/src/start/parse_cmdl.inc
similarity index 100%
rename from racket/src/racket/parse_cmdl.inc
rename to racket/src/start/parse_cmdl.inc
diff --git a/racket/src/start/win_single.inc b/racket/src/start/win_single.inc
new file mode 100644
index 0000000000..258b2121ec
--- /dev/null
+++ b/racket/src/start/win_single.inc
@@ -0,0 +1,169 @@
+/* ---------------------------------------- */
+/*        single-instance detection         */
+/* ---------------------------------------- */
+
+static char *CreateUniqueName()
+{
+  char desktop[MAX_PATH], session[32], *together;
+  int dlen, slen;
+
+  {
+    // Name should be desktop unique, so add current desktop name
+    HDESK hDesk;
+    ULONG cchDesk = MAX_PATH - 1;
+
+    hDesk = GetThreadDesktop(GetCurrentThreadId());
+    
+    if (!GetUserObjectInformation( hDesk, UOI_NAME, desktop, cchDesk, &cchDesk))
+      desktop[0] = 0;
+    else
+      desktop[MAX_PATH - 1]  = 0;
+  }
+
+  {
+    // Name should be session unique, so add current session id
+    HANDLE hToken = NULL;
+    // Try to open the token (fails on Win9x) and check necessary buffer size
+    if (OpenProcessToken(GetCurrentProcess(), TOKEN_QUERY, &hToken)) {
+      DWORD cbBytes = 0;
+      
+      if(!GetTokenInformation( hToken, TokenStatistics, NULL, cbBytes, &cbBytes ) 
+	 && GetLastError() == ERROR_INSUFFICIENT_BUFFER) {
+	  PTOKEN_STATISTICS pTS;
+
+	  pTS = (PTOKEN_STATISTICS)malloc(cbBytes);
+	  
+	  if(GetTokenInformation(hToken, TokenStatistics, (LPVOID)pTS, cbBytes, &cbBytes)) {
+	    sprintf(session, "-%08x%08x-",
+		    pTS->AuthenticationId.HighPart, 
+		    pTS->AuthenticationId.LowPart);
+	  } else
+	    session[0] = 0;
+	  free(pTS);
+      } else {
+	session[0] = 0;
+      }
+    } else
+      session[0] = 0;
+  }
+
+  dlen = strlen(desktop);
+  slen =  strlen(session);
+  together = (char *)malloc(slen + dlen + 1);
+  memcpy(together, desktop, dlen);
+  memcpy(together + dlen, session, slen);
+  together[dlen + slen] = 0;
+  
+  return together;
+}
+
+#define GRACKET_GUID "B2261834-D535-44dd-8511-A26FC8F97DD0"
+
+static int wm_is_gracket;
+
+static BOOL CALLBACK CheckWindow(HWND wnd, LPARAM param)
+{
+  int i, len, gl;
+  DWORD w;
+  char **argv, *v;
+  COPYDATASTRUCT cd;
+  DWORD_PTR result;
+  LRESULT ok;
+
+  ok = SendMessageTimeout(wnd, wm_is_gracket,
+			  0, 0, 
+			  SMTO_BLOCK |
+			  SMTO_ABORTIFHUNG,
+			  200,
+			  &result);
+
+  printf("try %p result %d\n", wnd, result);
+
+  if (ok == 0)
+    return TRUE; /* ignore and continue */
+  if ((intptr_t)result == 79) {
+    /* found it */
+  } else
+    return TRUE; /* continue search */
+
+  /* wnd is owned by another instance of this application */
+
+  SetForegroundWindow(wnd);
+  if (IsIconic(wnd)) 
+    ShowWindow(wnd, SW_RESTORE);
+
+  argv = (char **)param;
+  
+  len = gl = strlen(GRACKET_GUID);
+  len += 4 + sizeof(DWORD);
+  for (i = 1; argv[i]; i++) {
+    len += sizeof(DWORD) + strlen(argv[i]);
+  }
+  w = i - 1;
+
+  v = (char *)malloc(len);
+  memcpy(v, GRACKET_GUID, gl);
+  memcpy(v + gl, "OPEN", 4);
+  memcpy(v + gl + 4, &w, sizeof(DWORD));
+  len = gl + 4 + sizeof(DWORD);
+  for (i = 1; argv[i]; i++) {
+    w = strlen(argv[i]);
+    memcpy(v + len, &w, sizeof(DWORD));
+    len += sizeof(DWORD);
+    memcpy(v + len, argv[i], w);
+    len += w;
+  }
+
+  cd.dwData = 79;
+  cd.cbData = len;
+  cd.lpData = v;
+
+  SendMessage(wnd, WM_COPYDATA, (WPARAM)wnd, (LPARAM)&cd);
+
+  free(v);
+
+  return FALSE;
+}
+
+static int CheckSingleInstance(char *normalized_path, char **argv)
+{
+  /* Check for an existing instance: */
+  if (check_for_another[0] != 'n') {
+    int alreadyrunning;
+    HANDLE mutex;
+    int j, l, i;
+    char *a, *b;
+
+    /* This mutex creation synchronizes multiple instances of
+       the application that may have been started. */
+    j = strlen(normalized_path);
+    
+    b = CreateUniqueName();
+    l = strlen(b);
+    a = (char *)malloc(j + l + 50);
+    memcpy(a, normalized_path, j);
+    for (i = 0; i < j; i++) {
+      /* backslashes are not allowed in mutex names */
+      if (a[i] == '\\') a[i] = '/';
+    }
+    memcpy(a + j, b, l);
+    memcpy(a + j + l, "GRacket-" GRACKET_GUID, strlen(GRACKET_GUID) + 9);
+    mutex = CreateMutex(NULL, FALSE, a);
+    alreadyrunning = (GetLastError() == ERROR_ALREADY_EXISTS || 
+		      GetLastError() == ERROR_ACCESS_DENIED);
+    /* The call fails with ERROR_ACCESS_DENIED if the Mutex was 
+       created in a different users session because of passing
+       NULL for the SECURITY_ATTRIBUTES on Mutex creation. */
+    wm_is_gracket = RegisterWindowMessage(a);
+    free(a);
+
+    if (alreadyrunning) {
+      /* If another instance has been started, try to find it. */
+      if (!EnumWindows((WNDENUMPROC)CheckWindow, (LPARAM)argv)) {
+	return 1;
+      }
+    }
+  }
+
+  return 0;
+}
diff --git a/racket/src/worksp/cs/Makefile b/racket/src/worksp/cs/Makefile
index 95deb300c7..03545841c7 100644
--- a/racket/src/worksp/cs/Makefile
+++ b/racket/src/worksp/cs/Makefile
@@ -14,6 +14,11 @@ DEST = ..\..\build\raw_racketcs.exe
 GDEST = ..\..\build\raw_gracketcs.exe
 CSDIR = ..\..\cs\c
 
+MAIN_DEPS = ..\..\start\config.inc \
+            ..\..\start\parse_cmdl.inc \
+            ..\..\start\delayed.inc \
+            ..\..\start\win_single.inc
+
 FLAGS = /DWIN32
 COMP_SUBDIR = /DCS_COMPILED_SUBDIR=1
 
@@ -25,14 +30,14 @@ $(DEST_DLL): $(CSDIR)\boot.c libracket.res $(RKTIO_LIB)
 libracket.res: libracket.rc
 	rc /l 0x409 /folibracket.res libracket.rc
 
-$(DEST): $(CSDIR)\main.c $(DEST_DLL) racket.res
+$(DEST): $(CSDIR)\main.c $(MAIN_DEPS) $(DEST_DLL) racket.res
 	cl /Fe$(DEST) /Ox /MT $(COMP_SUBDIR) $(FLAGS) $(INCS) $(CSDIR)\main.c racket.res $(WIN32_LIBS)
 
 racket.res: ../racket/racket.rc ../racket/racket.ico
 	rc /l 0x409 /foracket.res ../racket/racket.rc
 
-$(GDEST): $(CSDIR)\grmain.c $(DEST_DLL) gracket.res
-	cl /Fe$(GDEST) /Ox /MT $(COMP_SUBDIR) $(FLAGS) $(INCS) $(CSDIR)\grmain.c gracket.res $(WIN32_LIBS) /subsystem:windows
+$(GDEST): $(CSDIR)\grmain.c $(CSDIR)\main.c $(MAIN_DEPS) $(DEST_DLL) gracket.res
+	cl /Fe$(GDEST) /Ox /MT $(COMP_SUBDIR) $(FLAGS) $(INCS) $(CSDIR)\grmain.c gracket.res $(WIN32_LIBS)
 
 gracket.res: ../gracket/gracket.rc ../gracket/gracket.ico
 	rc /l 0x409 /fogracket.res ../gracket/gracket.rc
diff --git a/racket/src/worksp/csbuild.rkt b/racket/src/worksp/csbuild.rkt
index 30333fa33f..8a2c94f2ac 100644
--- a/racket/src/worksp/csbuild.rkt
+++ b/racket/src/worksp/csbuild.rkt
@@ -11,6 +11,7 @@
 
 (define scheme-dir-provided? #f)
 (define abs-scheme-dir (build-path here 'up "build" "ChezScheme"))
+(define pull? #f)
 (define machine (if (= 32 (system-type 'word))
 		    "ti3nt"
 		    "ta6nt"))
@@ -25,6 +26,8 @@
                    (unless (equal? dir "")
                      (set! scheme-dir-provided? #t)
                      (set! abs-scheme-dir (path->complete-path dir)))]
+ [("--pull") "Use `git pull` on auto-cloned Chez Scheme repo"
+             (set! pull? #t)]
  [("--racketcs-suffix") str "Select the suffix for RacketCS"
                         (set! cs-suffix (string-upcase str))]
  [("--boot-mode") mode "Select the mode for Racket bootstrapping"
@@ -87,9 +90,10 @@
             scheme-dir
             git-clone-args)]))
 
-(unless scheme-dir-provided?
-  (parameterize ([current-directory scheme-dir])
-    (system*! "git" "pull")))
+(when pull?
+  (unless scheme-dir-provided?
+    (parameterize ([current-directory scheme-dir])
+      (system*! "git" "pull"))))
 
 (unless (file-exists? (build-path scheme-dir "zlib" "Makefile"))
   (parameterize ([current-directory scheme-dir])