diff --git a/H/rhstruct.h b/H/rhstruct.h
index 7b1dffb9c..7fa4f78f5 100644
--- a/H/rhstruct.h
+++ b/H/rhstruct.h
@@ -40,7 +40,7 @@
 #endif
 #if USE_DL_MALLOC || (USE_SYSTEM_MALLOC && HAVE_MALLINFO)
 #ifndef  HeapUsed
-#define  HeapUsed  Yap_givemallinfo()		
+#define  HeapUsed  Yap_givemallinfo()
 #endif
 
 #else
@@ -94,7 +94,6 @@
   CHTYPE_MODULE = AtomTermAdjust(CHTYPE_MODULE);
   TERMS_MODULE = AtomTermAdjust(TERMS_MODULE);
   SYSTEM_MODULE = AtomTermAdjust(SYSTEM_MODULE);
-  OPERATING_SYSTEM_MODULE = AtomTermAdjust(OPERATING_SYSTEM_MODULE);
   READUTIL_MODULE = AtomTermAdjust(READUTIL_MODULE);
   HACKS_MODULE = AtomTermAdjust(HACKS_MODULE);
   ARG_MODULE = AtomTermAdjust(ARG_MODULE);
diff --git a/library/system/sys.c b/library/system/sys.c
index 6cb0c7d73..f0fa979fd 100644
--- a/library/system/sys.c
+++ b/library/system/sys.c
@@ -89,6 +89,7 @@
 
 #include "config.h"
 #include "YapInterface.h"
+#include "crypto/md5.h"
 #include <stdlib.h>
 #if HAVE_UNISTD_H
 #include <unistd.h>
@@ -1072,28 +1073,52 @@ p_kill(void)
 #if HAVE_OPENSSL_RIPEMD_H
  #include <openssl/ripemd.h>
 #endif
-
+ 
 /** md5( +Text, -Key, -Remaining keyq
  * encode text using OpenSSL 
  *
- * arg Text as List of codes
- * arg2 and 3: difference list with character codes.
+ * arg Text is a List of ASCII codes
+ * arg2 and 3: difference list with the character codes for the
+ * digest.
  * 
  * @return whether ARG1's md5 unifies with the difference liat.
  */
  static YAP_Bool
    md5(void)
  {
-#if HAVE_OPENSSL_RIPEMD_H
-   char buf[21];
+   unsigned char buf[64];
+   md5_state_t pms;
+   const char *s;
+   size_t len = -1;
+   
+   if ( ! (s = YAP_StringToBuffer( YAP_ARG1 , NULL, len )) ||
+	s[0] == 0)
+     return false;
 
-   char *s = (char *) YAP_AllocSpaceFromYap(YAP_ListLength(YAP_ARG1)+1);
-   YAP_StringToBuffer( YAP_ARG1 , s, 20 ) ;
-   RIPEMD160((const unsigned char *)s, strlen(s), (unsigned char *)buf);
-   YAP_FreeSpaceFromYap(s);
-   return YAP_Unify( YAP_ARG2, YAP_BufferToDiffList( buf , YAP_ARG3 ) );
-#endif /* defined(__MINGW32__) || _MSC_VER */
-   return FALSE; 
+   md5_init( & pms );
+   md5_append( & pms, (const unsigned char *)s, strlen(s));
+   md5_finish( & pms, buf );
+   //free((void *)s);
+   YAP_Term t = YAP_ARG3;
+   int i = 16;
+   while (i > 0)
+     {
+       int top, bop;
+       i--;
+       top = buf[i]>>4;
+       if (top > 9)
+	 top = (top-10)+'a';
+       else
+	 top = top+'0';
+       bop = buf[i] & 15;
+       if (bop > 9)
+	 bop = (bop-10)+'a';
+       else
+	 bop = bop+'0';
+       t = YAP_MkPairTerm(YAP_MkIntTerm(top),
+			  YAP_MkPairTerm( YAP_MkIntTerm( bop ), t ));
+     }
+   return YAP_Unify( YAP_ARG2,t );
  }
 
 static YAP_Bool
@@ -1159,3 +1184,4 @@ int WINAPI win_sys(HANDLE hinst, DWORD reason, LPVOID reserved)
   return 1;
 }
 #endif
+                                                                                                                                                                                       
diff --git a/misc/HEAPFIELDS b/misc/HEAPFIELDS
index 05fae64d0..6fed9e53d 100644
--- a/misc/HEAPFIELDS
+++ b/misc/HEAPFIELDS
@@ -97,7 +97,6 @@ Term		charsio_module		CHARSIO_MODULE		MkAT AtomCharsio
 Term		chtype_module		CHTYPE_MODULE		MkAT AtomChType
 Term		terms_module		TERMS_MODULE		MkAT AtomTerms
 Term		system_module		SYSTEM_MODULE		MkAT AtomSystem
-Term		operating_system_module	OPERATING_SYSTEM_MODULE	MkAT AtomOperatingSystemSupport
 Term		readutil_module		READUTIL_MODULE		MkAT AtomReadutil
 Term		hacks_module		HACKS_MODULE		MkAT AtomYapHacks
 Term		arg_module		ARG_MODULE		MkAT AtomArg