diff --git a/Contrib/ExDLL/pluginapi.c b/Contrib/ExDLL/pluginapi.c
index 5d878606..3c459a9f 100644
--- a/Contrib/ExDLL/pluginapi.c
+++ b/Contrib/ExDLL/pluginapi.c
@@ -8,6 +8,8 @@
 #define COUNTOF(a) (sizeof(a)/sizeof(a[0]))
 #endif
 
+#define isvalidnsisvarindex(varnum) ( ((unsigned int)(varnum)) < (__INST_LAST) )
+
 unsigned int g_stringsize;
 stack_t **g_stacktop;
 TCHAR *g_variables;
@@ -48,13 +50,13 @@ void NSISCALL pushstring(const TCHAR *str)
 
 TCHAR* NSISCALL getuservariable(const int varnum)
 {
-  if (varnum < 0 || varnum >= __INST_LAST) return NULL;
+  if (!isvalidnsisvarindex(varnum)) return NULL;
   return g_variables+varnum*g_stringsize;
 }
 
 void NSISCALL setuservariable(const int varnum, const TCHAR *var)
 {
-	if (var != NULL && varnum >= 0 && varnum < __INST_LAST) 
+	if (var && isvalidnsisvarindex(varnum)) 
 		lstrcpy(g_variables + varnum*g_stringsize, var);
 }
 
@@ -100,7 +102,7 @@ void NSISCALL GetUserVariableA(const int varnum, char* ansiStr)
 
 void NSISCALL SetUserVariableA(const int varnum, const char* ansiStr)
 {
-   if (ansiStr != NULL && varnum >= 0 && varnum < __INST_LAST)
+   if (ansiStr && isvalidnsisvarindex(varnum))
    {
       wchar_t* wideStr = g_variables + varnum * g_stringsize;
       MultiByteToWideChar(CP_ACP, 0, ansiStr, -1, wideStr, g_stringsize);
@@ -149,7 +151,7 @@ void NSISCALL GetUserVariableA(const int varnum, char* ansiStr)
 
 void NSISCALL SetUserVariableW(const int varnum, const wchar_t* wideStr)
 {
-   if (wideStr != NULL && varnum >= 0 && varnum < __INST_LAST)
+   if (wideStr && isvalidnsisvarindex(varnum))
    {
       char* ansiStr = g_variables + varnum * g_stringsize;
       WideCharToMultiByte(CP_ACP, 0, wideStr, -1, ansiStr, g_stringsize, NULL, NULL);
diff --git a/Contrib/Library/RegTool/RegTool.c b/Contrib/Library/RegTool/RegTool.c
index d9fd981d..f40b6c49 100644
--- a/Contrib/Library/RegTool/RegTool.c
+++ b/Contrib/Library/RegTool/RegTool.c
@@ -265,6 +265,7 @@ HANDLE myOpenFile(const TCHAR *fn, DWORD da, DWORD cd)
   );
 }
 
+#ifndef _WIN64
 /** Modifies the wininit.ini file to rename / delete a file.
  *
  * @param prevName The previous / current name of the file.
@@ -364,6 +365,7 @@ void RenameViaWininit(const TCHAR* prevName, const TCHAR* newName)
     CloseHandle(hfile);
   }
 }
+#endif
 
 void DeleteFileOnReboot(TCHAR *pszFile)
 {
@@ -379,9 +381,10 @@ void DeleteFileOnReboot(TCHAR *pszFile)
       fOk=mfea(pszFile, NULL, MOVEFILE_DELAY_UNTIL_REBOOT);
     }
   }
-
+#ifndef _WIN64
   if (!fOk)
   {
     RenameViaWininit(pszFile, NULL);
   }
+#endif
 }
diff --git a/Contrib/Makensisw/makensisw.cpp b/Contrib/Makensisw/makensisw.cpp
index 04a64674..0ce10b0a 100644
--- a/Contrib/Makensisw/makensisw.cpp
+++ b/Contrib/Makensisw/makensisw.cpp
@@ -379,7 +379,7 @@ INT_PTR CALLBACK DialogProc(HWND hwndDlg, UINT msg, WPARAM wParam, LPARAM lParam
                 LogMessage(g_sdata.hwnd, g_sdata.compressor_stats);
               }
               DeleteFile(temp_file_name);
-              lstrcpy(g_sdata.compressor_stats,_T(""));
+              g_sdata.compressor_stats[0] = _T('\0');
             }
             else {
               g_sdata.compressor_name = compressor_names[this_compressor+1];
@@ -545,7 +545,7 @@ INT_PTR CALLBACK DialogProc(HWND hwndDlg, UINT msg, WPARAM wParam, LPARAM lParam
             l.lpstrFileTitle = NULL;
             l.lpstrInitialDir = NULL;
             l.Flags = OFN_HIDEREADONLY|OFN_EXPLORER|OFN_PATHMUSTEXIST|OFN_FILEMUSTEXIST;
-            lstrcpy(buf,_T(""));
+            buf[0] = _T('\0');
             if (GetOpenFileName(&l)) {
               SetScript(buf);
               PushMRUFile(g_sdata.script);
@@ -1176,7 +1176,7 @@ INT_PTR CALLBACK SymbolSetProc(HWND hwndDlg, UINT msg, WPARAM wParam, LPARAM lPa
           hwndEdit = FindWindowEx(GetDlgItem(hwndDlg, IDC_NAMES), 0, 0, 0); // Handle of list
           hwndEdit = FindWindowEx(GetDlgItem(hwndDlg, IDC_NAMES), hwndEdit, 0, 0); //Handle of edit box
           SendMessage(hwndEdit, WM_GETTEXT, (WPARAM)SYMBOL_SET_NAME_MAXLEN+1, (LPARAM)name);
-          if(!lstrlen(name)) {
+          if(!*name) {
             if(g_symbol_set_mode == 1) { //Load
               MessageBox(hwndDlg,LOAD_SYMBOL_SET_MESSAGE,LOAD_SYMBOL_SET_DLG_NAME,MB_OK|MB_ICONEXCLAMATION);
             }
diff --git a/Contrib/Makensisw/utils.cpp b/Contrib/Makensisw/utils.cpp
index ee9dd1a9..733b7541 100644
--- a/Contrib/Makensisw/utils.cpp
+++ b/Contrib/Makensisw/utils.cpp
@@ -268,12 +268,9 @@ void CompileNSISScript() {
     TCHAR *symbols = BuildSymbols();
     TCHAR compressor[40];
 
-    if(lstrlen(g_sdata.compressor_name)) {
+    compressor[0] = _T('\0');
+    if(*g_sdata.compressor_name)
       wsprintf(compressor,_T("/X\"SetCompressor /FINAL %s\""),g_sdata.compressor_name);
-    }
-    else {
-      lstrcpy(compressor,_T(""));
-    }
 
     TCHAR *args = (TCHAR *) GlobalLock(g_sdata.script_cmd_args);
 
diff --git a/Contrib/System/Source/Plugin.c b/Contrib/System/Source/Plugin.c
index f4d8f636..31744293 100644
--- a/Contrib/System/Source/Plugin.c
+++ b/Contrib/System/Source/Plugin.c
@@ -7,6 +7,8 @@
 
 HWND g_hwndParent;
 
+#define isvalidnsisvarindex(varnum) ( ((unsigned int)(varnum)) < (__INST_LAST) )
+
 TCHAR *AllocString()
 {
     return (TCHAR*) GlobalAlloc(GPTR,g_stringsize*sizeof(TCHAR));
@@ -46,14 +48,14 @@ TCHAR *system_pushstring(TCHAR *str)
 
 TCHAR *system_getuservariable(int varnum)
 {
-        if (varnum < 0 || varnum >= __INST_LAST) return AllocString();
+        if (!isvalidnsisvarindex(varnum)) return AllocString();
         return AllocStr(g_variables+varnum*g_stringsize);
 }
 
 TCHAR *system_setuservariable(int varnum, TCHAR *var)
 {
-        if (var != NULL && varnum >= 0 && varnum < __INST_LAST) {
-                lstrcpy (g_variables + varnum*g_stringsize, var);
+        if (var && isvalidnsisvarindex(varnum)) {
+                lstrcpy(g_variables + varnum*g_stringsize, var);
         }
         return var;
 }
diff --git a/Contrib/System/Source/System.c b/Contrib/System/Source/System.c
index 053517e6..c2185b04 100644
--- a/Contrib/System/Source/System.c
+++ b/Contrib/System/Source/System.c
@@ -379,18 +379,25 @@ PLUGINFUNCTION(Call)
 PLUGINFUNCTIONSHORT(Int64Op)
 {
     __int64 i1, i2 = 0, i3, i4;
-    TCHAR *op, *o1, *o2;
-    TCHAR buf[128];
+    TCHAR *op;
+#ifndef _WIN64
+    TCHAR buf[25], *o1, *o2;
+#endif
 
-    // Get strings
-    o1 = system_popstring(); op = system_popstring(); 
-    i1 = myatoi64(o1); // convert first arg to int64
+    // Get parameters: <num1> <op> [num2]
+#ifdef _WIN64
+    i1 = system_popintptr();
+#else
+    o1 = system_popstring(), i1 = myatoi64(o1);
+#endif
+    op = system_popstring();
     if ((*op != _T('~')) && (*op != _T('!')))
     {
-        // get second arg, convert it, free it
-        o2 = system_popstring();
-        i2 = myatoi64(o2); 
-        GlobalFree(o2);
+#ifdef _WIN64
+        i2 = system_popintptr();
+#else
+        o2 = system_popstring(), i2 = myatoi64(o2), GlobalFree(o2);
+#endif
     }
 
     // operation
@@ -418,9 +425,12 @@ PLUGINFUNCTIONSHORT(Int64Op)
     }
     
     // Output and freedom
-    myitoa64(i1, buf);
-    system_pushstring(buf);
-    GlobalFree(o1); GlobalFree(op);
+#ifdef _WIN64
+    system_pushintptr(i1);
+#else
+    myitoa64(i1, buf), system_pushstring(buf), GlobalFree(o1);
+#endif
+    GlobalFree(op);
 } PLUGINFUNCTIONEND
 
 __int64 GetIntFromString(TCHAR **p)
diff --git a/Source/Platform.h b/Source/Platform.h
index 6604d2d6..48e6d503 100644
--- a/Source/Platform.h
+++ b/Source/Platform.h
@@ -83,7 +83,7 @@ typedef HANDLE HMODULE;
 typedef unsigned long HKEY;
 // some gdi
 typedef DWORD COLORREF;
-typedef UINT32 HBRUSH;
+typedef HANDLE HBRUSH;
 // bool
 #  define FALSE 0
 #  define TRUE 1
diff --git a/Source/build.cpp b/Source/build.cpp
index 7cf32494..3fbaea24 100644
--- a/Source/build.cpp
+++ b/Source/build.cpp
@@ -2316,7 +2316,7 @@ void CEXEBuild::AddStandardStrings()
   }
 #endif//NSIS_CONFIG_UNINSTALL_SUPPORT
 #ifdef NSIS_SUPPORT_MOVEONREBOOT
-  cur_header->str_wininit = add_asciistring(_T("$WINDIR\\wininit.ini"));
+  cur_header->str_wininit = is_target_64bit() ? 0 : add_asciistring(_T("$WINDIR\\wininit.ini"));
 #endif//NSIS_SUPPORT_MOVEONREBOOT
 }
 
@@ -2816,7 +2816,7 @@ int CEXEBuild::write_output(void)
 
   if (db_opt_save)
   {
-    UINT32 total_out_size_estimate=
+    size_t total_out_size_estimate=
       m_exehead_size+sizeof(fh)+build_datablock.getlen()+(build_crcchk?sizeof(crc32_t):0);
     int pc=(int)((db_opt_save*1000)/(db_opt_save+total_out_size_estimate));
     FriendlySize fs(db_opt_save);
diff --git a/Source/exehead/Main.c b/Source/exehead/Main.c
index 557648fa..08032c77 100644
--- a/Source/exehead/Main.c
+++ b/Source/exehead/Main.c
@@ -320,14 +320,14 @@ end:
     BOOL (WINAPI *OPT)(HANDLE, DWORD,PHANDLE);
     BOOL (WINAPI *LPV)(LPCTSTR,LPCTSTR,PLUID);
     BOOL (WINAPI *ATP)(HANDLE,BOOL,PTOKEN_PRIVILEGES,DWORD,PTOKEN_PRIVILEGES,PDWORD);
-    #ifndef _WIN64
+    #ifdef _WIN64
+    OPT=OpenProcessToken, LPV=LookupPrivilegeValue, ATP=AdjustTokenPrivileges;
+    #else
     OPT=myGetProcAddress(MGA_OpenProcessToken);
     LPV=myGetProcAddress(MGA_LookupPrivilegeValue);
     ATP=myGetProcAddress(MGA_AdjustTokenPrivileges);
-    #else
-    OPT=OpenProcessToken, LPV=LookupPrivilegeValue, ATP=AdjustTokenPrivileges;
-    #endif
     if (OPT && LPV && ATP)
+    #endif
     {
       HANDLE hToken;
       TOKEN_PRIVILEGES tkp;
diff --git a/Source/exehead/Ui.c b/Source/exehead/Ui.c
index 41aaea98..8e7b06dd 100644
--- a/Source/exehead/Ui.c
+++ b/Source/exehead/Ui.c
@@ -236,16 +236,17 @@ FORCE_INLINE int NSISCALL ui_doinstall(void)
 
   LANGID (WINAPI *GUDUIL)();
 
-  #ifndef _WIN64
-  GUDUIL = myGetProcAddress(MGA_GetUserDefaultUILanguage);
-  #else
+#ifdef _WIN64
   GUDUIL = GetUserDefaultUILanguage;
-  #endif
+#else
+  GUDUIL = myGetProcAddress(MGA_GetUserDefaultUILanguage);
   if (GUDUIL)
+#endif
   {
     // Windows ME/2000+
     myitoa(state_language, GUDUIL());
   }
+#ifndef _WIN64
   else
   {
     static const TCHAR reg_9x_locale[]     = _T("Control Panel\\Desktop\\ResourceLocale");
@@ -270,6 +271,7 @@ FORCE_INLINE int NSISCALL ui_doinstall(void)
 
     mystrcat(state_language, g_tmp);
   }
+#endif
 
   // set default language
   set_language();
diff --git a/Source/exehead/util.c b/Source/exehead/util.c
index 12b2af0c..650d41b4 100644
--- a/Source/exehead/util.c
+++ b/Source/exehead/util.c
@@ -457,6 +457,7 @@ BOOL NSISCALL myReadFile(HANDLE h, LPVOID buf, DWORD cb)
 }
 
 #ifdef NSIS_SUPPORT_MOVEONREBOOT
+#ifndef _WIN64
 /** Modifies the wininit.ini file to rename / delete a file.
  *
  * @param prevName The previous / current name of the file.
@@ -555,6 +556,7 @@ void RenameViaWininit(const TCHAR* prevName, const TCHAR* newName)
     CloseHandle(hfile);
   }
 }
+#endif
 
 /**
  * MoveFileOnReboot tries to move a file by the name of pszExisting to the
@@ -577,11 +579,12 @@ void NSISCALL MoveFileOnReboot(LPCTSTR pszExisting, LPCTSTR pszNew)
   {
     fOk=mfea(pszExisting, pszNew, MOVEFILE_DELAY_UNTIL_REBOOT|MOVEFILE_REPLACE_EXISTING);
   }
-  
-  if (!fOk && sizeof(void*) <= 4)
+#ifndef _WIN64
+  if (!fOk)
   {
     RenameViaWininit(pszExisting, pszNew);
   }
+#endif
 
 #ifdef NSIS_SUPPORT_REBOOT
   g_exec_flags.exec_reboot++;
@@ -610,7 +613,7 @@ void NSISCALL myRegGetStr(HKEY root, const TCHAR *sub, const TCHAR *name, TCHAR
 void NSISCALL iptrtostr(TCHAR *s, INT_PTR d)
 {
 #ifdef _WIN64
-  static const TCHAR c[] = _T("%I64d"); 
+  static const TCHAR c[] = _T("%Id"); 
 #else
   static const TCHAR c[] = _T("%d");
 #endif
diff --git a/Source/script.cpp b/Source/script.cpp
index c81a78ad..40f6344a 100644
--- a/Source/script.cpp
+++ b/Source/script.cpp
@@ -723,8 +723,11 @@ void CEXEBuild::ps_addtoline(const TCHAR *str, GrowBuf &linedata, StringList &hi
               if (t)
               {
                 UINT32 codpts[]={utf32,UNICODE_REPLACEMENT_CHARACTER,'?'};
-                for(UINT i=0; i < COUNTOF(codpts); ++i)
-                  if (WCFromCodePoint(dyndefbuf,COUNTOF(dyndefbuf),codpts[i])) break;
+                for(size_t i=0, cch; i < COUNTOF(codpts); ++i)
+                {
+                  cch = WCFromCodePoint(dyndefbuf,COUNTOF(dyndefbuf),codpts[i]);
+                  if (cch) { dyndefbuf[cch] = _T('\0'); break; }
+                }
                 t=dyndefbuf;
               }
             }
diff --git a/Source/strlist.cpp b/Source/strlist.cpp
index f9861caa..097a2f6e 100644
--- a/Source/strlist.cpp
+++ b/Source/strlist.cpp
@@ -160,7 +160,7 @@ unsigned int ExeHeadStringList::find(const void *ptr, unsigned int cchF, WORD co
     else 
       delete[] bufMB;
   }
-  return retval;
+  return BUGBUG64TRUNCATE(unsigned int, retval);
 }
 
 int ExeHeadStringList::add(const TCHAR *str, WORD codepage, bool processed)
diff --git a/Source/tchar.h b/Source/tchar.h
index 57bc21ad..fee30bf7 100644
--- a/Source/tchar.h
+++ b/Source/tchar.h
@@ -58,7 +58,7 @@ typedef wchar_t TCHAR, _TUCHAR;
 #define _tprintf    wprintf
 #define _vftprintf  vfwprintf
 #define _vsntprintf _vsnwprintf
-#if defined(_MSC_VER) && (_MSC_VER<=1310)
+#if defined(_MSC_VER) && (_MSC_VER<=1310||_MSC_FULL_VER<=140040310)
 #	define _vstprintf  vswprintf
 #else
 #	define _vstprintf  _vswprintf
@@ -242,10 +242,11 @@ typedef unsigned char   _TUCHAR;
 
 #endif
 
-// is functions (the same in Unicode / ANSI)
-#ifndef _istgraph
-#define _istgraph   isgraph
-#endif
+// is functions (the same in Unicode / ANSI on MinGW? MSVC does not agree!)
 #ifndef _istascii
-#define _istascii   __isascii
+#if defined(_MSC_VER) && defined(_UNICODE)
+#define _istascii iswascii
+#else
+#define _istascii __isascii
+#endif
 #endif