--- a/hal/windows/WindowsBattery.cpp
+++ b/hal/windows/WindowsBattery.cpp
@@ -1,54 +1,29 @@
 /* -*- Mode: C++; tab-width: 2; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
 /* 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/. */
 
 #include "Hal.h"
 #include "HalImpl.h"
-#include "nsITimer.h"
 #include "mozilla/Preferences.h"
 #include "mozilla/dom/battery/Constants.h"
-#include "nsComponentManagerUtils.h"
 
 #include <windows.h>
-#include "mozilla/WindowsVersion.h"
 
 using namespace mozilla::dom::battery;
 
 namespace mozilla {
 namespace hal_impl {
 
-static nsCOMPtr<nsITimer> sUpdateTimer;
-
-/* Power Event API is Vista or later */
-static decltype(RegisterPowerSettingNotification)* sRegisterPowerSettingNotification = nullptr;
-static decltype(UnregisterPowerSettingNotification)* sUnregisterPowerSettingNotification = nullptr;
 static HPOWERNOTIFY sPowerHandle = nullptr;
 static HPOWERNOTIFY sCapacityHandle = nullptr;
 static HWND sHWnd = nullptr;
 
-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;
-
-  hal_impl::GetCurrentBatteryInformation(&currentInfo);
-  if (sLastInfo.level() != currentInfo.level() ||
-      sLastInfo.charging() != currentInfo.charging() ||
-      sLastInfo.remainingTime() != currentInfo.remainingTime()) {
-    hal::NotifyBatteryChange(currentInfo);
-    sLastInfo = currentInfo;
-  }
-}
-
 static
 LRESULT CALLBACK
 BatteryWindowProc(HWND hwnd, UINT msg, WPARAM wParam, LPARAM lParam) {
   if (msg != WM_POWERBROADCAST || wParam != PBT_POWERSETTINGCHANGE) {
     return DefWindowProc(hwnd, msg, wParam, lParam);
   }
 
   hal::BatteryInformation currentInfo;
@@ -58,104 +33,66 @@ BatteryWindowProc(HWND hwnd, UINT msg, W
 
   hal::NotifyBatteryChange(currentInfo);
   return TRUE;
 }
 
 void
 EnableBatteryNotifications()
 {
-  if (IsVistaOrLater()) {
-    // RegisterPowerSettingNotification is from Vista or later.
-    // Use this API if available.
-    HMODULE hUser32 = GetModuleHandleW(L"USER32.DLL");
-    if (!sRegisterPowerSettingNotification)
-      sRegisterPowerSettingNotification = (decltype(RegisterPowerSettingNotification)*)
-        GetProcAddress(hUser32, "RegisterPowerSettingNotification");
-    if (!sUnregisterPowerSettingNotification)
-      sUnregisterPowerSettingNotification = (decltype(UnregisterPowerSettingNotification)*)
-        GetProcAddress(hUser32, "UnregisterPowerSettingNotification");
+  // Create custom window to watch battery event
+  // If we can get Gecko's window handle, this is unnecessary.
+
+  if (sHWnd == nullptr) {
+    WNDCLASSW wc;
+    HMODULE hSelf = GetModuleHandle(nullptr);
 
-    if (!sRegisterPowerSettingNotification ||
-        !sUnregisterPowerSettingNotification) {
-      NS_ASSERTION(false, "Canot find PowerSettingNotification functions.");
-      return;
+    if (!GetClassInfoW(hSelf, L"MozillaBatteryClass", &wc)) {
+      ZeroMemory(&wc, sizeof(WNDCLASSW));
+      wc.hInstance = hSelf;
+      wc.lpfnWndProc = BatteryWindowProc;
+      wc.lpszClassName = L"MozillaBatteryClass";
+      RegisterClassW(&wc);
     }
 
-    // Create custom window to watch battery event
-    // If we can get Gecko's window handle, this is unnecessary.
-
-    if (sHWnd == nullptr) {
-      WNDCLASSW wc;
-      HMODULE hSelf = GetModuleHandle(nullptr);
+    sHWnd = CreateWindowW(L"MozillaBatteryClass", L"Battery Watcher",
+                          0, 0, 0, 0, 0,
+                          nullptr, nullptr, hSelf, nullptr);
+  }
 
-      if (!GetClassInfoW(hSelf, L"MozillaBatteryClass", &wc)) {
-        ZeroMemory(&wc, sizeof(WNDCLASSW));
-        wc.hInstance = hSelf;
-        wc.lpfnWndProc = BatteryWindowProc;
-        wc.lpszClassName = L"MozillaBatteryClass";
-        RegisterClassW(&wc);
-      }
-
-      sHWnd = CreateWindowW(L"MozillaBatteryClass", L"Battery Watcher",
-                            0, 0, 0, 0, 0,
-                            nullptr, nullptr, hSelf, nullptr);
-    }
+  if (sHWnd == nullptr) {
+    return;
+  }
 
-    if (sHWnd == nullptr) {
-      return;
-    }
-
-    sPowerHandle =
-      sRegisterPowerSettingNotification(sHWnd,
-                                        &GUID_ACDC_POWER_SOURCE,
-                                        DEVICE_NOTIFY_WINDOW_HANDLE);
-    sCapacityHandle =
-      sRegisterPowerSettingNotification(sHWnd,
-                                        &GUID_BATTERY_PERCENTAGE_REMAINING,
-                                        DEVICE_NOTIFY_WINDOW_HANDLE);
-  } else
-  {
-    // for Windows XP.  If we remove Windows XP support,
-    // we should remove timer-based power notification
-    sUpdateTimer = do_CreateInstance(NS_TIMER_CONTRACTID);
-    if (sUpdateTimer) {
-      sUpdateTimer->InitWithFuncCallback(UpdateHandler,
-                                         nullptr,
-                                         Preferences::GetInt("dom.battery.timer",
-                                                             30000 /* 30s */),
-                                         nsITimer::TYPE_REPEATING_SLACK);
-    } 
-  }
+  sPowerHandle =
+    RegisterPowerSettingNotification(sHWnd,
+                                     &GUID_ACDC_POWER_SOURCE,
+                                     DEVICE_NOTIFY_WINDOW_HANDLE);
+  sCapacityHandle =
+    RegisterPowerSettingNotification(sHWnd,
+                                     &GUID_BATTERY_PERCENTAGE_REMAINING,
+                                     DEVICE_NOTIFY_WINDOW_HANDLE);
 }
 
 void
 DisableBatteryNotifications()
 {
-  if (IsVistaOrLater()) {
-    if (sPowerHandle) {
-      sUnregisterPowerSettingNotification(sPowerHandle);
-      sPowerHandle = nullptr;
-    }
-
-    if (sCapacityHandle) {
-      sUnregisterPowerSettingNotification(sCapacityHandle);
-      sCapacityHandle = nullptr;
-    }
+  if (sPowerHandle) {
+    UnregisterPowerSettingNotification(sPowerHandle);
+    sPowerHandle = nullptr;
+  }
 
-    if (sHWnd) {
-      DestroyWindow(sHWnd);
-      sHWnd = nullptr;
-    }
-  } else
-  {
-    if (sUpdateTimer) {
-      sUpdateTimer->Cancel();
-      sUpdateTimer = nullptr;
-    }
+  if (sCapacityHandle) {
+    UnregisterPowerSettingNotification(sCapacityHandle);
+    sCapacityHandle = nullptr;
+  }
+
+  if (sHWnd) {
+    DestroyWindow(sHWnd);
+    sHWnd = nullptr;
   }
 }
 
 void
 GetCurrentBatteryInformation(hal::BatteryInformation* aBatteryInfo)
 {
   SYSTEM_POWER_STATUS status;
   if (!GetSystemPowerStatus(&status)) {