diff --git a/msvc/Makefile.msvc6 b/msvc/Makefile.msvc6
index 6968a2453..d54ac7111 100644
--- a/msvc/Makefile.msvc6
+++ b/msvc/Makefile.msvc6
@@ -61,6 +61,7 @@ SUBDIR        = c gc gmp
 LIBRARIES     =
 LSP_LIBRARIES = cmp.fas clx.fas sysfun.lsp
 TARGETS       = ecl.exe
+DEF           = ecl.def
 # Define here the processor type to compile GMP library
 # with maximum optimization. Possible values are:
 # 	gc -> generic implementation
@@ -68,6 +69,16 @@ TARGETS       = ecl.exe
 # 	p3 -> Pentium III processor
 # 	p4 -> Pentium IV processor
 GMP_TYPE      = gc
+# Set it to non-empty to include Win32 thread support
+ECL_THREADS   =
+
+!if "$(ECL_THREADS)" == ""
+ENV_EXPORT = cl_env,DATA
+!else
+ENV_EXPORT = ecl_process_env
+CFLAGS     = $(CFLAGS) -DECL_THREADS
+DEF        = ecl-threads.def
+!endif
 
 all:	$(TARGETS) doc ecl-config.bat
 .PHONY:	all
@@ -116,6 +127,7 @@ compile.lsp: bare.lsp $(srcdir)/compile.lsp.in Makefile.msvc6
 	    -e "s,@LIBEXT@,lib,g" \
 	    -e "s,@EXEEXT@,.exe,g" \
 	    -e "s,@LDINSTALLNAME@,,g" \
+	    -e "s,@DEF@,$(DEF),g" \
 	    < $(srcdir)\compile.lsp.in > compile.lsp
 bare.lsp: $(srcdir)/bare.lsp.in lsp/load.lsp clos/load.lsp cmp/load.lsp cmp/cmpcfg.lsp
 	sed -e "s,@true_srcdir@,$(srcdir:\=/),g" \
@@ -156,11 +168,11 @@ ecl-config.bat: util\ecl-config.bat Makefile.msvc6
 
 eclmin.lib: eclgmp.lib eclgc.lib lsp/config.lsp
 	cd c
-	$(MAKE) -f Makefile.msvc6
+	$(MAKE) -f Makefile.msvc6 "ECL_THREADS = $(ECL_THREADS)"
 	cd ..
 eclgc.lib:
 	cd gc
-	$(MAKE) -f Makefile.msvc6 gc.lib
+	$(MAKE) -f Makefile.msvc6 "ECL_THREADS = $(ECL_THREADS)" gc.lib
 	$(CP) gc.lib ..\eclgc.lib
 	cd ..
 	for %h in (gc.h gc_local_alloc.h gc_pthread_redirects.h \
@@ -190,6 +202,7 @@ install-base:
 	for %i in ($(TARGETS) ecl.dll) do $(CP) %i $(bindir)\%i
 	$(CP) ecl-config.bat $(bindir)\ecl-config.bat
 	for %i in ($(LSP_LIBRARIES) $(LIBRARIES) c\dpp.exe help.doc ecl.lib) do $(CP) %i $(libdir)
+	for %i in (ecl-s.lib ecl-full-s.lib) do IF EXIST %i $(CP) %i $(libdir)
 	$(CP) h\config.h $(libdir)\h
 flatinstall:
 	$(MAKE) -f Makefile.msvc6 bindir=$(prefix) libdir=$(prefix) install-base
diff --git a/msvc/c/Makefile.msvc6 b/msvc/c/Makefile.msvc6
index 57c0ad2a5..a70e6ffc2 100644
--- a/msvc/c/Makefile.msvc6
+++ b/msvc/c/Makefile.msvc6
@@ -4,14 +4,23 @@
 top_srcdir = ..\..\src
 srcdir	= ..\..\src\c
 
+!if "$(ECL_THREADS)" != ""
+THREADS_OBJ= threads_win32.obj
+THREADS_FLAGS= -DECL_THREADS -DGC_WIN32_THREADS
+!else
+THREADS_OBJ=
+THREADS_FLAGS=
+!endif
+
 # Programs used by "make":
 #
 TRUE_CC = cl
 CC	= cl
-CFLAGS	= -c -Zi -I./ -I$(srcdir) -I$(HDIR) -I../h -I$(top_srcdir)/gc/include -DHAVE_ISATTY
+CFLAGS	= -c -Zi -I./ -I$(srcdir) -I$(HDIR) -I../h -I$(top_srcdir)/gc/include -DHAVE_ISATTY $(THREADS_FLAGS)
 #	  -Wall -W -Wfloat-equal -Wundef -Wendif-labels -Wpointer-arith -Wcast-align \
 #	  -Wwrite-strings -Wconversion -Wsign-compare -Wmissing-prototypes -Wredundant-decls \
 #	  -Wunreachable-code -Winline
+DEFS    = $(THREADS_FLAGS)
 
 SHELL	= /bin/sh
 RM	= del
@@ -49,7 +58,7 @@ OBJS	= main.obj symbol.obj package.obj list.obj\
 	time.obj unixint.obj\
 	mapfun.obj multival.obj hash.obj format.obj pathname.obj\
 	structure.obj load.obj unixfsys.obj unixsys.obj \
-	ffi.obj alloc_2.obj tcp.obj
+	ffi.obj alloc_2.obj tcp.obj $(THREADS_OBJ)
 
 all:	$(DPP) external.h ..\eclmin.lib ..\cinit.obj
 
@@ -57,6 +66,8 @@ all:	$(DPP) external.h ..\eclmin.lib ..\cinit.obj
 
 {$(srcdir:\=/)}.d{}.c:
 	$(DPP) $< $@
+#.d.c:
+#	$(DPP) $< $@
 .c.obj:
 	$(CC) $(CFLAGS) -o $@ $<
 
diff --git a/msvc/gc/Makefile.msvc6 b/msvc/gc/Makefile.msvc6
index 309ebec1a..3444cecc1 100644
--- a/msvc/gc/Makefile.msvc6
+++ b/msvc/gc/Makefile.msvc6
@@ -7,15 +7,23 @@ CPU= i386
 
 srcdir = ..\..\src\gc
 
-OBJS= alloc.obj reclaim.obj allchblk.obj misc.obj mach_dep.obj os_dep.obj mark_rts.obj headers.obj mark.obj obj_map.obj blacklst.obj finalize.obj new_hblk.obj dbg_mlc.obj malloc.obj stubborn.obj dyn_load.obj typd_mlc.obj ptr_chck.obj gc_cpp.obj mallocx.obj
+!if "$(ECL_THREADS)" != ""
+THREADS_OBJ= win32_threads.obj
+THREADS_FLAGS= -DGC_WIN32_THREADS
+!else
+THREADS_OBJ=
+THREADS_FLAGS=
+!endif
+
+OBJS= alloc.obj reclaim.obj allchblk.obj misc.obj mach_dep.obj os_dep.obj mark_rts.obj headers.obj mark.obj obj_map.obj blacklst.obj finalize.obj new_hblk.obj dbg_mlc.obj malloc.obj stubborn.obj dyn_load.obj typd_mlc.obj ptr_chck.obj gc_cpp.obj mallocx.obj $(THREADS_OBJ)
 
 all: gctest.exe cord\de.exe test_cpp.exe
 
 {$(srcdir)}.c{}.obj:
-	$(cc) $(cdebug) $(cflags) $(cvars) -I$(srcdir)\include -DSILENT -DALL_INTERIOR_POINTERS -D__STDC__ -DGC_NOT_DLL $< /Fo$*.obj
+	$(cc) $(cdebug) $(cflags) $(cvars) -I$(srcdir)\include -DSILENT -DALL_INTERIOR_POINTERS -D__STDC__ -DGC_NOT_DLL $(THREADS_FLAGS) $< /Fo$*.obj
 
 .cpp.obj:
-	$(cc) $(cdebug) $(cflags) $(cvars) -I$(srcdir)\include -DSILENT -DALL_INTERIOR_POINTERS -DGC_NOT_DLL $*.CPP /Fo$*.obj
+	$(cc) $(cdebug) $(cflags) $(cvars) -I$(srcdir)\include -DSILENT -DALL_INTERIOR_POINTERS -DGC_NOT_DLL $(THREADS_FLAGS) $*.CPP /Fo$*.obj
 
 $(OBJS) tests\test.obj: $(srcdir)\include\private\gc_priv.h $(srcdir)\include\private\gc_hdrs.h $(srcdir)\include\gc.h $(srcdir)\include\private\gcconfig.h $(srcdir)\include\private\gc_locks.h $(srcdir)\include\private\gc_pmark.h $(srcdir)\include\gc_mark.h
 
diff --git a/msvc/h/config.h.msvc6 b/msvc/h/config.h.msvc6
index 42c08917f..95c07d412 100644
--- a/msvc/h/config.h.msvc6
+++ b/msvc/h/config.h.msvc6
@@ -26,10 +26,13 @@
 #endif
 
 /* Userland threads?							*/
-#undef ECL_THREADS
+/* #undef ECL_THREADS */
 
 /* Network streams							*/
 #define TCP 1
+#if defined(TCP) && (defined(_MSC_VER) || defined(mingw32))
+# define ECL_WSOCK
+#endif
 
 /* Foreign functions interface						*/
 #define ECL_FFI
diff --git a/src/c/time.d b/src/c/time.d
index 657c3e96d..f2a4935b0 100644
--- a/src/c/time.d
+++ b/src/c/time.d
@@ -27,7 +27,7 @@
 
 #if defined(mignw32) || defined(_MSC_VER)
 /* The function sleep() in MinGW is bogus: it counts millisecons! */
-#include <winbase.h>
+#include <windows.h>
 #define sleep(x) Sleep(x*1000)
 #endif