--- a/dom/plugins/base/nsNPAPIPlugin.cpp
+++ b/dom/plugins/base/nsNPAPIPlugin.cpp
@@ -88,16 +88,17 @@ using mozilla::PluginPRLibrary;
 using mozilla::plugins::PluginModuleParent;
 
 #ifdef MOZ_X11
 #include "mozilla/X11Util.h"
 #endif
 
 #ifdef XP_WIN
 #include <windows.h>
+#include "nsWindowsHelpers.h"
 #endif
 
 #ifdef MOZ_WIDGET_ANDROID
 #include <android/log.h>
 #include "android_npapi.h"
 #include "ANPBase.h"
 #include "AndroidBridge.h"
 #define LOG(args...)  __android_log_print(ANDROID_LOG_INFO, "GeckoPlugins" , ## args)
@@ -276,30 +277,16 @@ static bool GMA9XXGraphics()
       }
     }
     ::CGLDestroyRendererInfo(renderer);
   }
   return hasIntelGMA9XX;
 }
 #endif
 
-#ifdef XP_WIN
-static bool
-IsVistaOrLater()
-{
-  OSVERSIONINFO info;
-
-  ZeroMemory(&info, sizeof(OSVERSIONINFO));
-  info.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
-  GetVersionEx(&info);
-
-  return info.dwMajorVersion >= 6;
-}
-#endif
-
 bool
 nsNPAPIPlugin::RunPluginOOP(const nsPluginTag *aPluginTag)
 {
   if (PR_GetEnv("MOZ_DISABLE_OOP_PLUGINS")) {
     return false;
   }
 
   if (!aPluginTag) {

--- a/hal/windows/WindowsBattery.cpp
+++ b/hal/windows/WindowsBattery.cpp
@@ -5,16 +5,17 @@
 
 #include "Hal.h"
 #include "HalImpl.h"
 #include "nsITimer.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/dom/battery/Constants.h"
 
 #include <windows.h>
+#include "nsWindowsHelpers.h"
 
 using namespace mozilla::dom::battery;
 
 namespace mozilla {
 namespace hal_impl {
 
 static nsCOMPtr<nsITimer> sUpdateTimer;
 
@@ -22,28 +23,16 @@ static nsCOMPtr<nsITimer> sUpdateTimer;
 typedef HPOWERNOTIFY (WINAPI *REGISTERPOWERSETTINGNOTIFICATION) (HANDLE, LPCGUID, DWORD);
 typedef BOOL (WINAPI *UNREGISTERPOWERSETTINGNOTIFICATION) (HPOWERNOTIFY);
 static REGISTERPOWERSETTINGNOTIFICATION sRegisterPowerSettingNotification = nsnull;
 static UNREGISTERPOWERSETTINGNOTIFICATION sUnregisterPowerSettingNotification = nsnull;
 static HPOWERNOTIFY sPowerHandle = nsnull;
 static HPOWERNOTIFY sCapacityHandle = nsnull;
 static HWND sHWnd = nsnull;
 
-static bool
-IsVistaOrLater()
-{
-  OSVERSIONINFO info;
-
-  ZeroMemory(&info, sizeof(OSVERSIONINFO));
-  info.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
-  GetVersionEx(&info);
-
-  return info.dwMajorVersion >= 6;
-}
-
 static void
 UpdateHandler(nsITimer* aTimer, void* aClosure) {
   NS_ASSERTION(!IsVistaOrLater(),
                "We shouldn't call this function for Vista or later version!");
 
   static hal::BatteryInformation sLastInfo;
   hal::BatteryInformation currentInfo;
 

--- a/toolkit/xre/nsWindowsDllBlocklist.cpp
+++ b/toolkit/xre/nsWindowsDllBlocklist.cpp
@@ -14,16 +14,17 @@
 #include "nsXULAppAPI.h"
 
 #include "nsAutoPtr.h"
 #include "nsThreadUtils.h"
 
 #include "prlog.h"
 
 #include "nsWindowsDllInterceptor.h"
+#include "nsWindowsHelpers.h"
 
 using namespace mozilla;
 
 #if defined(MOZ_CRASHREPORTER) && !defined(NO_BLOCKLIST_CRASHREPORTER)
 #include "nsExceptionHandler.h"
 #endif
 
 #define ALL_VERSIONS   ((unsigned long long)-1LL)
@@ -151,28 +152,16 @@ struct RVAMap {
   operator const T*() const { return mMappedView; }
   const T* operator->() const { return mMappedView; }
 private:
   const T* mMappedView;
   void* mRealView;
 };
 
 bool
-IsVistaOrLater()
-{
-  OSVERSIONINFO info;
-
-  ZeroMemory(&info, sizeof(OSVERSIONINFO));
-  info.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
-  GetVersionEx(&info);
-
-  return info.dwMajorVersion >= 6;
-}
-
-bool
 CheckASLR(const wchar_t* path)
 {
   bool retval = false;
 
   HANDLE file = ::CreateFileW(path, GENERIC_READ, FILE_SHARE_READ,
                               NULL, OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL,
                               NULL);
   if (file != INVALID_HANDLE_VALUE) {

--- a/xpcom/base/nsWindowsHelpers.h
+++ b/xpcom/base/nsWindowsHelpers.h
@@ -1,15 +1,16 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
 
 #ifndef nsWindowsHelpers_h
 #define nsWindowsHelpers_h
 
+#include <windows.h>
 #include "nsAutoRef.h"
 #include "nscore.h"
 
 template<>
 class nsAutoRefTraits<HKEY>
 {
 public:
   typedef HKEY RawRef;
@@ -77,9 +78,22 @@ public:
   }
   RawRef mRawRef;
 };
 
 typedef nsAutoRef<HKEY> nsAutoRegKey;
 typedef nsAutoRef<SC_HANDLE> nsAutoServiceHandle;
 typedef nsAutoRef<HANDLE> nsAutoHandle;
 
+namespace
+{
+  bool
+  IsVistaOrLater()
+  {
+    OSVERSIONINFO info;
+    ZeroMemory(&info, sizeof(OSVERSIONINFO));
+    info.dwOSVersionInfoSize = sizeof(OSVERSIONINFO);
+    GetVersionEx(&info);
+    return info.dwMajorVersion >= 6;
+  }
+}
+
 #endif