diff --git a/gfx/thebes/gfxGDIFontList.cpp b/gfx/thebes/gfxGDIFontList.cpp
index 4a1d71dc4675..6475dd511a02 100644
--- a/gfx/thebes/gfxGDIFontList.cpp
+++ b/gfx/thebes/gfxGDIFontList.cpp
@@ -29,7 +29,6 @@
 
 #include "mozilla/MemoryReporting.h"
 #include "mozilla/Telemetry.h"
-#include "mozilla/WindowsVersion.h"
 
 #include <usp10.h>
 
diff --git a/mfbt/WindowsVersion.h b/mfbt/WindowsVersion.h
index 4156f4f64baa..1d27ce5bdf91 100644
--- a/mfbt/WindowsVersion.h
+++ b/mfbt/WindowsVersion.h
@@ -84,81 +84,6 @@ IsWindowsBuildOrLater(uint32_t aBuild)
   return false;
 }
 
-#if defined(_M_X64) || defined(_M_AMD64)
-// We support only Win7 or later on Win64.
-MOZ_ALWAYS_INLINE bool
-IsXPSP3OrLater()
-{
-  return true;
-}
-
-MOZ_ALWAYS_INLINE bool
-IsWin2003OrLater()
-{
-  return true;
-}
-
-MOZ_ALWAYS_INLINE bool
-IsWin2003SP2OrLater()
-{
-  return true;
-}
-
-MOZ_ALWAYS_INLINE bool
-IsVistaOrLater()
-{
-  return true;
-}
-
-MOZ_ALWAYS_INLINE bool
-IsVistaSP1OrLater()
-{
-  return true;
-}
-
-MOZ_ALWAYS_INLINE bool
-IsWin7OrLater()
-{
-  return true;
-}
-#else
-MOZ_ALWAYS_INLINE bool
-IsXPSP3OrLater()
-{
-  return IsWindowsVersionOrLater(0x05010300ul);
-}
-
-MOZ_ALWAYS_INLINE bool
-IsWin2003OrLater()
-{
-  return IsWindowsVersionOrLater(0x05020000ul);
-}
-
-MOZ_ALWAYS_INLINE bool
-IsWin2003SP2OrLater()
-{
-  return IsWindowsVersionOrLater(0x05020200ul);
-}
-
-MOZ_ALWAYS_INLINE bool
-IsVistaOrLater()
-{
-  return IsWindowsVersionOrLater(0x06000000ul);
-}
-
-MOZ_ALWAYS_INLINE bool
-IsVistaSP1OrLater()
-{
-  return IsWindowsVersionOrLater(0x06000100ul);
-}
-
-MOZ_ALWAYS_INLINE bool
-IsWin7OrLater()
-{
-  return IsWindowsVersionOrLater(0x06010000ul);
-}
-#endif
-
 MOZ_ALWAYS_INLINE bool
 IsWin7SP1OrLater()
 {
@@ -186,8 +111,7 @@ IsWin10OrLater()
 MOZ_ALWAYS_INLINE bool
 IsNotWin7PreRTM()
 {
-  return IsWin7SP1OrLater() || !IsWin7OrLater() ||
-         IsWindowsBuildOrLater(7600);
+  return IsWin7SP1OrLater() || IsWindowsBuildOrLater(7600);
 }
 
 } // namespace mozilla
diff --git a/widget/LookAndFeel.h b/widget/LookAndFeel.h
index 397cc052b8fb..c2403d30de34 100644
--- a/widget/LookAndFeel.h
+++ b/widget/LookAndFeel.h
@@ -418,10 +418,7 @@ public:
    * Operating system versions.
    */
   enum OperatingSystemVersion {
-    // XXX: The XP and Vista values can now be removed (see bug 1330146).
-    eOperatingSystemVersion_WindowsXP = 0,
-    eOperatingSystemVersion_WindowsVista,
-    eOperatingSystemVersion_Windows7,
+    eOperatingSystemVersion_Windows7 = 2,
     eOperatingSystemVersion_Windows8,
     eOperatingSystemVersion_Windows10,
     eOperatingSystemVersion_Unknown
diff --git a/widget/windows/KeyboardLayout.cpp b/widget/windows/KeyboardLayout.cpp
index c711e71f81f3..921788a143ed 100644
--- a/widget/windows/KeyboardLayout.cpp
+++ b/widget/windows/KeyboardLayout.cpp
@@ -10,7 +10,6 @@
 #include "mozilla/MouseEvents.h"
 #include "mozilla/MiscEvents.h"
 #include "mozilla/TextEvents.h"
-#include "mozilla/WindowsVersion.h"
 
 #include "nsAlgorithm.h"
 #ifdef MOZ_CRASHREPORTER
diff --git a/widget/windows/WinMessages.h b/widget/windows/WinMessages.h
index e722a38360d9..d0613cb15e1e 100644
--- a/widget/windows/WinMessages.h
+++ b/widget/windows/WinMessages.h
@@ -45,10 +45,6 @@
 #define MOZ_WM_DEADCHAR                   (WM_APP+0x031E)
 #define MOZ_WM_SYSDEADCHAR                (WM_APP+0x031F)
 
-// Internal message for ensuring the file picker is visible on multi monitor
-// systems, and when the screen resolution changes.
-#define MOZ_WM_ENSUREVISIBLE              (WM_APP+0x374F)
-
 // XXX Should rename them to MOZ_WM_* and use safer values!
 // Messages for fullscreen transition window
 #define WM_FULLSCREEN_TRANSITION_BEFORE   (WM_USER + 0)
diff --git a/widget/windows/WinMouseScrollHandler.cpp b/widget/windows/WinMouseScrollHandler.cpp
index e157b1be2d2f..fc3e38eb69ed 100644
--- a/widget/windows/WinMouseScrollHandler.cpp
+++ b/widget/windows/WinMouseScrollHandler.cpp
@@ -20,7 +20,6 @@
 #include "mozilla/MiscEvents.h"
 #include "mozilla/MouseEvents.h"
 #include "mozilla/Preferences.h"
-#include "mozilla/WindowsVersion.h"
 
 #include <psapi.h>
 
diff --git a/widget/windows/WinTaskbar.cpp b/widget/windows/WinTaskbar.cpp
index aa2c6b313f9f..699dc96f6dfb 100644
--- a/widget/windows/WinTaskbar.cpp
+++ b/widget/windows/WinTaskbar.cpp
@@ -28,7 +28,6 @@
 #include "nsPIDOMWindow.h"
 #include "nsAppDirectoryServiceDefs.h"
 #include "mozilla/Preferences.h"
-#include "mozilla/WindowsVersion.h"
 #include <io.h>
 #include <propvarutil.h>
 #include <propkey.h>
diff --git a/widget/windows/nsDataObj.cpp b/widget/windows/nsDataObj.cpp
index 5454a791e9ca..96f1aae93337 100644
--- a/widget/windows/nsDataObj.cpp
+++ b/widget/windows/nsDataObj.cpp
@@ -38,7 +38,6 @@
 
 #include "WinUtils.h"
 #include "mozilla/LazyIdleThread.h"
-#include "mozilla/WindowsVersion.h"
 #include <algorithm>
 
 
diff --git a/widget/windows/nsFilePicker.cpp b/widget/windows/nsFilePicker.cpp
index d304996ff136..a634acddef99 100644
--- a/widget/windows/nsFilePicker.cpp
+++ b/widget/windows/nsFilePicker.cpp
@@ -37,8 +37,6 @@ using namespace mozilla::widget;
 char16_t *nsFilePicker::mLastUsedUnicodeDirectory;
 char nsFilePicker::mLastUsedDirectory[MAX_PATH+1] = { 0 };
 
-static const wchar_t kDialogPtrProp[] = L"DialogPtrProperty";
-static const DWORD kDialogTimerID = 9999;
 static const unsigned long kDialogTimerTimeout = 300;
 
 #define MAX_EXTENSION_LENGTH 10