diff --git a/src/core/concurrent/qtconcurrentiteratekernel.cpp b/src/core/concurrent/qtconcurrentiteratekernel.cpp
index afb8bd2f8..977b487d3 100644
--- a/src/core/concurrent/qtconcurrentiteratekernel.cpp
+++ b/src/core/concurrent/qtconcurrentiteratekernel.cpp
@@ -41,19 +41,11 @@
 
 #include "qtconcurrentiteratekernel.h"
 
-#if defined(Q_OS_MAC)
-#include <mach/mach.h>
-#include <mach/mach_time.h>
-#include <unistd.h>
-#elif defined(Q_OS_UNIX)
 #if defined(Q_OS_HURD)
 #include <sys/time.h>
 #endif
 #include <time.h>
 #include <unistd.h>
-#elif defined(Q_OS_WIN)
-#include <qt_windows.h>
-#endif
 
 #include "qfunctions_p.h"
 
@@ -66,16 +58,6 @@ enum {
     MedianSize = 7
 };
 
-#if defined(Q_OS_MAC)
-
-static qint64 getticks()
-{
-    return mach_absolute_time();
-}
-
-#elif defined(Q_OS_UNIX)
-
-
 static qint64 getticks()
 {
 #if defined(_POSIX_TIMERS) && (_POSIX_TIMERS > 0)
@@ -115,19 +97,7 @@ static qint64 getticks()
 #endif
 }
 
-#elif defined(Q_OS_WIN)
-
-static qint64 getticks()
-{
-    LARGE_INTEGER x;
-    if (!QueryPerformanceCounter(&x))
-        return 0;
-    return x.QuadPart;
-}
-
-#endif
-
-static double elapsed(qint64 after, qint64 before)
+static inline double elapsed(qint64 after, qint64 before)
 {
     return double(after - before);
 }
diff --git a/src/core/global/qconfig.h.cmake b/src/core/global/qconfig.h.cmake
index 940d98289..4be70f92c 100644
--- a/src/core/global/qconfig.h.cmake
+++ b/src/core/global/qconfig.h.cmake
@@ -75,6 +75,10 @@
 #define QT_NO_QWS_VNC
 #define QT_NO_AUDIO_BACKEND
 #define QT_NO_DIRECTWRITE
+#define QT_NO_STYLE_WINDOWSCE
+#define QT_NO_STYLE_WINDOWSMOBILE
+#define QT_NO_STYLE_WINDOWSXP
+#define QT_NO_STYLE_WINDOWSVISTA
 
 /* Qt build specs */
 #ifndef QT_EDITION
@@ -209,10 +213,6 @@
 #cmakedefine QT_NO_STYLE_CLEANLOOKS
 #cmakedefine QT_NO_STYLE_PLASTIQUE
 #cmakedefine QT_NO_STYLE_STYLESHEET
-#cmakedefine QT_NO_STYLE_WINDOWSCE
-#cmakedefine QT_NO_STYLE_WINDOWSMOBILE
-#cmakedefine QT_NO_STYLE_WINDOWSVISTA
-#cmakedefine QT_NO_STYLE_WINDOWSXP
 
 /* Utilities */
 #cmakedefine QT_NO_ACCESSIBILITY
diff --git a/src/core/global/qfeatures.h b/src/core/global/qfeatures.h
index 46cf5c019..e7ec44957 100644
--- a/src/core/global/qfeatures.h
+++ b/src/core/global/qfeatures.h
@@ -229,9 +229,6 @@
 // QMotifStyle
 //#define QT_NO_STYLE_MOTIF
 
-// QWindowsStyle
-//#define QT_NO_STYLE_WINDOWS
-
 // QSystemSemaphore
 //#define QT_NO_SYSTEMSEMAPHORE
 
@@ -385,11 +382,6 @@
 #define QT_NO_STYLE_CDE
 #endif
 
-// QWindowsXPStyle
-#if !defined(QT_NO_STYLE_WINDOWSXP) && (defined(QT_NO_STYLE_WINDOWS))
-#define QT_NO_STYLE_WINDOWSXP
-#endif
-
 // QToolButton
 #if !defined(QT_NO_TOOLBUTTON) && (defined(QT_NO_ACTION))
 #define QT_NO_TOOLBUTTON
@@ -450,11 +442,6 @@
 #define QT_NO_SCROLLAREA
 #endif
 
-// QWindowsVistaStyle
-#if !defined(QT_NO_STYLE_WINDOWSVISTA) && (defined(QT_NO_STYLE_WINDOWSXP))
-#define QT_NO_STYLE_WINDOWSVISTA
-#endif
-
 // QTabBar
 #if !defined(QT_NO_TABBAR) && (defined(QT_NO_TOOLBUTTON))
 #define QT_NO_TABBAR
@@ -530,16 +517,6 @@
 #define QT_NO_STYLE_STYLESHEET
 #endif
 
-// QWindowsCEStyle
-#if !defined(QT_NO_STYLE_WINDOWSCE) && (defined(QT_NO_STYLE_WINDOWS) || defined(QT_NO_IMAGEFORMAT_XPM))
-#define QT_NO_STYLE_WINDOWSCE
-#endif
-
-// QWindowsMobileStyle
-#if !defined(QT_NO_STYLE_WINDOWSMOBILE) && (defined(QT_NO_STYLE_WINDOWS) || defined(QT_NO_IMAGEFORMAT_XPM))
-#define QT_NO_STYLE_WINDOWSMOBILE
-#endif
-
 // QtSvg module
 #if !defined(QT_NO_SVG) && (defined(QT_NO_XMLSTREAMREADER) || defined(QT_NO_CSSPARSER))
 #define QT_NO_SVG
diff --git a/src/core/io/qfilesystemwatcher.cpp b/src/core/io/qfilesystemwatcher.cpp
index c1f440532..fcd3f3d96 100644
--- a/src/core/io/qfilesystemwatcher.cpp
+++ b/src/core/io/qfilesystemwatcher.cpp
@@ -239,16 +239,12 @@ void QPollingFileSystemWatcherEngine::timeout()
 
 QFileSystemWatcherEngine *QFileSystemWatcherPrivate::createNativeEngine()
 {
-#if defined(Q_OS_WIN)
-    return new QWindowsFileSystemWatcherEngine;
-#elif defined(Q_OS_QNX) && !defined(QT_NO_INOTIFY)
-    return QInotifyFileSystemWatcherEngine::create();
-#elif defined(Q_OS_LINUX)
+#if defined(Q_OS_LINUX)
     QFileSystemWatcherEngine *eng = QInotifyFileSystemWatcherEngine::create();
     if(!eng)
         eng = QDnotifyFileSystemWatcherEngine::create();
     return eng;
-#elif defined(Q_OS_FREEBSD) || defined(Q_OS_MAC)
+#elif defined(Q_OS_FREEBSD)
         return QKqueueFileSystemWatcherEngine::create();
 #else
     return 0;
diff --git a/src/core/io/qfsfileengine.cpp b/src/core/io/qfsfileengine.cpp
index 96bc7cb92..f0dc81f29 100644
--- a/src/core/io/qfsfileengine.cpp
+++ b/src/core/io/qfsfileengine.cpp
@@ -433,7 +433,6 @@ qint64 QFSFileEngine::size() const
     return d->nativeSize();
 }
 
-#ifndef Q_OS_WIN
 /*!
     \internal
 */
@@ -448,7 +447,6 @@ qint64 QFSFileEnginePrivate::sizeFdFh() const
         return 0;
     return metaData.size();
 }
-#endif
 
 /*!
     \reimp
@@ -683,11 +681,7 @@ qint64 QFSFileEnginePrivate::writeFdFh(const char *data, qint64 len)
     } else if (fd != -1) {
         // Unbuffered stdio mode.
 
-#ifdef Q_OS_WIN
-        int result;
-#else
         ssize_t result;
-#endif
         do {
             result = QT_WRITE(fd, data + writtenBytes, size_t(len - writtenBytes));
         } while ((result == -1 && errno == EINTR)
diff --git a/src/core/io/qfsfileengine_p.h b/src/core/io/qfsfileengine_p.h
index 2059abb12..68d484fc5 100644
--- a/src/core/io/qfsfileengine_p.h
+++ b/src/core/io/qfsfileengine_p.h
@@ -119,10 +119,8 @@ public:
     mutable uint is_sequential : 2;
     mutable uint could_stat : 1;
     mutable uint tried_stat : 1;
-#if !defined(Q_OS_WINCE)
     mutable uint need_lstat : 1;
     mutable uint is_link : 1;
-#endif
 
     bool doStat(QFileSystemMetaData::MetaDataFlags flags = QFileSystemMetaData::PosixStatFlags) const;
     bool isSymlink() const;
diff --git a/src/core/io/qprocess_p.h b/src/core/io/qprocess_p.h
index d5cf29a4f..fc94e846d 100644
--- a/src/core/io/qprocess_p.h
+++ b/src/core/io/qprocess_p.h
@@ -118,19 +118,6 @@ class QProcessEnvironmentPrivate: public QSharedData
 public:
     typedef QProcEnvKey Key;
     typedef QProcEnvValue Value;
-#ifdef Q_OS_WIN
-    inline Key prepareName(const QString &name) const { return Key(name); }
-    inline QString nameToString(const Key &name) const { return name; }
-    inline Value prepareValue(const QString &value) const { return value; }
-    inline QString valueToString(const Value &value) const { return value; }
-    struct MutexLocker {
-        MutexLocker(const QProcessEnvironmentPrivate *) {}
-    };
-    struct OrderedMutexLocker {
-        OrderedMutexLocker(const QProcessEnvironmentPrivate *,
-                           const QProcessEnvironmentPrivate *) {}
-    };
-#else
     inline Key prepareName(const QString &name) const
     {
         Key &ent = nameMap[name];
@@ -177,17 +164,14 @@ public:
         hash.detach();
         nameMap.detach();
     }
-#endif
 
     typedef QHash<Key, Value> Hash;
     Hash hash;
 
-#ifdef Q_OS_UNIX
     typedef QHash<QString, Key> NameHash;
     mutable NameHash nameMap;
 
     mutable QMutex mutex;
-#endif
 
     static QProcessEnvironment fromList(const QStringList &list);
     QStringList toList() const;
diff --git a/src/core/io/qstandardpaths.cpp b/src/core/io/qstandardpaths.cpp
index 1d3f3816c..002fc6072 100644
--- a/src/core/io/qstandardpaths.cpp
+++ b/src/core/io/qstandardpaths.cpp
@@ -292,18 +292,6 @@ QStringList QStandardPaths::locateAll(StandardLocation type, const QString &file
    return result;
 }
 
-#ifdef Q_OS_WIN
-static QStringList executableExtensions()
-{
-   // If %PATHEXT% does not contain .exe, it is either empty, malformed, or distorted in ways that we cannot support, anyway.
-   const QStringList pathExt = QString::fromLocal8Bit(qgetenv("PATHEXT")).toLower().split(QLatin1Char(';'));
-   return pathExt.contains(QLatin1String(".exe"), Qt::CaseInsensitive) ?
-          pathExt :
-          QStringList() << QLatin1String(".exe") << QLatin1String(".com")
-          << QLatin1String(".bat") << QLatin1String(".cmd");
-}
-#endif
-
 static QString checkExecutable(const QString &path)
 {
    const QFileInfo info(path);
@@ -327,30 +315,6 @@ static inline QString searchExecutable(const QStringList &searchPaths,
    return QString();
 }
 
-#ifdef Q_OS_WIN
-
-// Find executable appending candidate suffixes, used for suffix-less executables
-// on Windows.
-static inline QString
-searchExecutableAppendSuffix(const QStringList &searchPaths,
-                             const QString &executableName,
-                             const QStringList &suffixes)
-{
-   const QDir currentDir = QDir::current();
-   foreach (const QString & searchPath, searchPaths) {
-      const QString candidateRoot = currentDir.absoluteFilePath(searchPath + QLatin1Char('/') + executableName);
-      foreach (const QString & suffix, suffixes) {
-         const QString absPath = checkExecutable(candidateRoot + suffix);
-         if (!absPath.isEmpty()) {
-            return absPath;
-         }
-      }
-   }
-   return QString();
-}
-
-#endif // Q_OS_WIN
-
 /*!
   Finds the executable named \a executableName in the paths specified by \a paths,
   or the system paths if \a paths is empty.
@@ -378,12 +342,8 @@ QString QStandardPaths::findExecutable(const QString &executableName, const QStr
 
    QStringList searchPaths = paths;
    if (paths.isEmpty()) {
-      QByteArray pEnv = qgetenv("PATH");
-#if defined(Q_OS_WIN)
-      const QLatin1Char pathSep(';');
-#else
+      const QByteArray pEnv = qgetenv("PATH");
       const QLatin1Char pathSep(':');
-#endif
       // Remove trailing slashes, which occur on Windows.
       const QStringList rawPaths = QString::fromLocal8Bit(pEnv.constData()).split(pathSep, QString::SkipEmptyParts);
       searchPaths.reserve(rawPaths.size());
@@ -396,19 +356,6 @@ QString QStandardPaths::findExecutable(const QString &executableName, const QStr
       }
    }
 
-#ifdef Q_OS_WIN
-   // On Windows, if the name does not have a suffix or a suffix not
-   // in PATHEXT ("xx.foo"), append suffixes from PATHEXT.
-   static const QStringList executable_extensions = executableExtensions();
-   if (executableName.contains(QLatin1Char('.'))) {
-      const QString suffix = QFileInfo(executableName).suffix();
-      if (suffix.isEmpty() || !executable_extensions.contains(QLatin1Char('.') + suffix, Qt::CaseInsensitive)) {
-         return searchExecutableAppendSuffix(searchPaths, executableName, executable_extensions);
-      }
-   } else {
-      return searchExecutableAppendSuffix(searchPaths, executableName, executable_extensions);
-   }
-#endif
    return searchExecutable(searchPaths, executableName);
 }
 
@@ -419,7 +366,6 @@ QString QStandardPaths::findExecutable(const QString &executableName, const QStr
     an empty QString if no relevant location can be found.
 */
 
-#if !defined(Q_OS_MAC)
 QString QStandardPaths::displayName(StandardLocation type)
 {
    switch (type) {
@@ -461,7 +407,6 @@ QString QStandardPaths::displayName(StandardLocation type)
    // not reached
    return QString();
 }
-#endif
 
 QT_END_NAMESPACE
 
diff --git a/src/core/kernel/qsystemsemaphore.cpp b/src/core/kernel/qsystemsemaphore.cpp
index 9a28e7d5a..73fac96cd 100644
--- a/src/core/kernel/qsystemsemaphore.cpp
+++ b/src/core/kernel/qsystemsemaphore.cpp
@@ -235,7 +235,7 @@ void QSystemSemaphore::setKey(const QString &key, int initialValue, AccessMode m
         return;
     d->error = NoError;
     d->errorString = QString();
-#if !defined(Q_OS_WIN) && !defined(QT_POSIX_IPC)
+#if !defined(QT_POSIX_IPC)
     // optimization to not destroy/create the file & semaphore
     if (key == d->key && mode == Create && d->createdSemaphore && d->createdFile) {
         d->initialValue = initialValue;
diff --git a/src/core/kernel/qsystemsemaphore_p.h b/src/core/kernel/qsystemsemaphore_p.h
index cda23f4c9..1b6788b18 100644
--- a/src/core/kernel/qsystemsemaphore_p.h
+++ b/src/core/kernel/qsystemsemaphore_p.h
@@ -58,9 +58,8 @@
 #ifndef QT_NO_SYSTEMSEMAPHORE
 
 #include "qsharedmemory_p.h"
-#ifndef Q_OS_WINCE
-#  include <sys/types.h>
-#endif
+
+#include <sys/types.h>
 #ifdef QT_POSIX_IPC
 #  include <semaphore.h>
 #endif
@@ -78,10 +77,7 @@ public:
         return QSharedMemoryPrivate::makePlatformSafeKey(key, QLatin1String("qipc_systemsem_"));
     }
 
-#ifdef Q_OS_WIN
-    HANDLE handle(QSystemSemaphore::AccessMode mode = QSystemSemaphore::Open);
-    void setErrorString(const QString &function);
-#elif defined(QT_POSIX_IPC)
+#if defined(QT_POSIX_IPC)
     bool handle(QSystemSemaphore::AccessMode mode = QSystemSemaphore::Open);
     void setErrorString(const QString &function);
 #else
@@ -94,10 +90,7 @@ public:
     QString key;
     QString fileName;
     int initialValue;
-#ifdef Q_OS_WIN
-    HANDLE semaphore;
-    HANDLE semaphoreLock;
-#elif defined(QT_POSIX_IPC)
+#if defined(QT_POSIX_IPC)
     sem_t *semaphore;
     bool createdSemaphore;
 #else
diff --git a/src/core/plugin/qpluginloader.h b/src/core/plugin/qpluginloader.h
index a470a3c1a..ad3802724 100644
--- a/src/core/plugin/qpluginloader.h
+++ b/src/core/plugin/qpluginloader.h
@@ -44,11 +44,6 @@
 
 #include <QtCore/qlibrary.h>
 
-#if defined(QT_NO_LIBRARY) && defined(Q_OS_WIN)
-#undef QT_NO_LIBRARY
-#pragma message("QT_NO_LIBRARY is not supported on Windows")
-#endif
-
 #ifndef QT_NO_LIBRARY
 
 QT_BEGIN_HEADER
diff --git a/src/core/tools/qlocale_tools.cpp b/src/core/tools/qlocale_tools.cpp
index 035c3b06e..3af33d89b 100644
--- a/src/core/tools/qlocale_tools.cpp
+++ b/src/core/tools/qlocale_tools.cpp
@@ -254,13 +254,6 @@ bool removeGroupSeparators(QLocalePrivate::CharBuff *num)
     return true;
 }
 
-#if defined(Q_CC_MWERKS) && defined(Q_OS_WIN32)
-inline bool isascii(int c)
-{
-        return (c >= 0 && c <=127);
-}
-#endif
-
 /*-
  * Copyright (c) 1992, 1993
  *        The Regents of the University of California.  All rights reserved.
@@ -557,11 +550,11 @@ __RCSID("$NetBSD: strtod.c,v 1.26 1998/02/03 18:44:21 perry Exp $");
 #endif /* LIBC_SCCS and not lint */
 
 /*
-#if defined(__m68k__)    || defined(__sparc__) || defined(__i386__) || \
-     defined(__mips__)    || defined(__ns32k__) || defined(__alpha__) || \
-     defined(__powerpc__) || defined(Q_OS_WIN) || defined(Q_OS_DARWIN) || defined(Q_OS_MAC) || \
-     defined(mips) || defined(Q_OS_AIX) || defined(Q_OS_SOLARIS)
-#           define IEEE_BIG_OR_LITTLE_ENDIAN 1
+#if defined(__m68k__)    || defined(__sparc__) || defined(__i386__)  || \
+    defined(__mips__)    || defined(__ns32k__) || defined(__alpha__) || \
+    defined(__powerpc__) || defined(mips)      || defined(Q_OS_AIX)  || \
+    defined(Q_OS_SOLARIS)
+#       define IEEE_BIG_OR_LITTLE_ENDIAN 1
 #endif
 */
 
@@ -2253,14 +2246,6 @@ static int quorem(Bigint *b, Bigint *S)
  *           calculation.
  */
 
-#if defined(Q_OS_WIN) && defined (Q_CC_GNU) && !defined(_clear87) // See QTBUG-7576
-extern "C" {
-__attribute__ ((dllimport)) unsigned int __cdecl __MINGW_NOTHROW _control87 (unsigned int unNew, unsigned int unMask);
-__attribute__ ((dllimport)) unsigned int __cdecl __MINGW_NOTHROW _clearfp (void); /* Clear the FPU status word */
-}
-#  define _clear87 _clearfp
-#endif
-
 /* This actually sometimes returns a pointer to a string literal
    cast to a char*. Do NOT try to modify the return value. */
 
diff --git a/src/core/tools/qstring.cpp b/src/core/tools/qstring.cpp
index 3e5891711..6dac44d3d 100644
--- a/src/core/tools/qstring.cpp
+++ b/src/core/tools/qstring.cpp
@@ -58,18 +58,7 @@
 #include "qdebug.h"
 #include "qendian.h"
 #include "qmutex.h"
-
-#ifdef Q_OS_MAC
-#include <qcore_mac_p.h>
-#endif
-
-#include <qfunctions_p.h>
-
-#if defined(Q_OS_WINCE)
-#include <windows.h>
-#include <winnls.h>
-#endif
-
+#include "qfunctions_p.h"
 
 #include <limits.h>
 #include <string.h>
@@ -4574,12 +4563,6 @@ int QString::localeAwareCompare(const QString &other) const
     return localeAwareCompare_helper(constData(), length(), other.constData(), other.length());
 }
 
-#if defined(Q_OS_WIN32) || defined(Q_OS_WINCE)
-QT_END_NAMESPACE
-#include "qt_windows.h"
-QT_BEGIN_NAMESPACE
-#endif
-
 /*!
     \internal
     \since 4.5
@@ -4591,50 +4574,19 @@ int QString::localeAwareCompare_helper(const QChar *data1, int length1,
     if (length1 == 0 || length2 == 0)
         return ucstrcmp(data1, length1, data2, length2);
 
-#if defined(Q_OS_WIN32) || defined(Q_OS_WINCE)
-    int res = CompareString(GetUserDefaultLCID(), 0, (wchar_t*)data1, length1, (wchar_t*)data2, length2);
-
-    switch (res) {
-    case CSTR_LESS_THAN:
-        return -1;
-    case CSTR_GREATER_THAN:
-        return 1;
-    default:
-        return 0;
-    }
-#elif defined (Q_OS_MAC)
-    // Use CFStringCompare for comparing strings on Mac. This makes Qt order
-    // strings the same way as native applications do, and also respects
-    // the "Order for sorted lists" setting in the International preferences
-    // panel.
-    const CFStringRef thisString =
-        CFStringCreateWithCharactersNoCopy(kCFAllocatorDefault,
-            reinterpret_cast<const UniChar *>(data1), length1, kCFAllocatorNull);
-    const CFStringRef otherString =
-        CFStringCreateWithCharactersNoCopy(kCFAllocatorDefault,
-            reinterpret_cast<const UniChar *>(data2), length2, kCFAllocatorNull);
-
-    const int result = CFStringCompare(thisString, otherString, kCFCompareLocalized);
-    CFRelease(thisString);
-    CFRelease(otherString);
-    return result;
-#elif defined(Q_OS_UNIX)
-#  if defined(QT_USE_ICU)
+#if defined(QT_USE_ICU)
     int res;
     if (qt_ucol_strcoll(data1, length1, data2, length2, &res)) {
         if (res == 0)
             res = ucstrcmp(data1, length1, data2, length2);
         return res;
     } // else fall through
-#  endif
+#endif
     // declared in <string.h>
     int delta = strcoll(toLocal8Bit_helper(data1, length1), toLocal8Bit_helper(data2, length2));
     if (delta == 0)
         delta = ucstrcmp(data1, length1, data2, length2);
     return delta;
-#else
-    return ucstrcmp(data1, length1, data2, length2);
-#endif
 }
 
 
@@ -5233,11 +5185,7 @@ QString &QString::vsprintf(const char* cformat, va_list ap)
             }
             case 'p': {
                 void *arg = va_arg(ap, void*);
-#ifdef Q_OS_WIN64
-                quint64 i = reinterpret_cast<quint64>(arg);
-#else
                 quint64 i = reinterpret_cast<unsigned long>(arg);
-#endif
                 flags |= QLocalePrivate::Alternate;
                 subst = locale.d()->unsLongLongToString(i, precision, 16, width, flags);
                 ++c;