diff --git a/xpcom/io/SpecialSystemDirectory.cpp b/xpcom/io/SpecialSystemDirectory.cpp
index 43fc27cc938..a59686324cd 100644
--- a/xpcom/io/SpecialSystemDirectory.cpp
+++ b/xpcom/io/SpecialSystemDirectory.cpp
@@ -19,6 +19,9 @@
 #include <shlobj.h>
 #include <knownfolders.h>
 #include <guiddef.h>
+#include "mozilla/WindowsVersion.h"
+
+using mozilla::IsWin7OrLater;
 
 #elif defined(XP_OS2)
 
@@ -155,10 +158,7 @@ GetLibrarySaveToPath(int aFallbackFolderId, REFKNOWNFOLDERID aFolderId,
                      nsIFile** aFile)
 {
     // Skip off checking for library support if the os is Vista or lower.
-    DWORD dwVersion = GetVersion();
-    if ((DWORD)(LOBYTE(LOWORD(dwVersion))) < 6 ||
-        ((DWORD)(LOBYTE(LOWORD(dwVersion))) == 6 &&
-         (DWORD)(HIBYTE(LOWORD(dwVersion))) == 0))
+    if (!IsWin7OrLater())
       return GetWindowsFolder(aFallbackFolderId, aFile);
 
     nsRefPtr<IShellLibrary> shellLib;
diff --git a/xpcom/io/nsLocalFileWin.cpp b/xpcom/io/nsLocalFileWin.cpp
index 3d1e3e01ab0..223b4bd0c51 100644
--- a/xpcom/io/nsLocalFileWin.cpp
+++ b/xpcom/io/nsLocalFileWin.cpp
@@ -5,6 +5,7 @@
 
 #include "mozilla/DebugOnly.h"
 #include "mozilla/Util.h"
+#include "mozilla/WindowsVersion.h"
 
 #include "nsCOMPtr.h"
 #include "nsAutoPtr.h"
@@ -1834,10 +1835,8 @@ nsLocalFile::CopySingleFile(nsIFile *sourceFile, nsIFile *destParent,
     // Copying a 1KB file without COPY_FILE_NO_BUFFERING takes < 1ms.
     // So we only use COPY_FILE_NO_BUFFERING when we have a remote drive.
     int copyOK;
-    DWORD dwVersion = GetVersion();
-    DWORD dwMajorVersion = (DWORD)(LOBYTE(LOWORD(dwVersion)));
     DWORD dwCopyFlags = COPY_FILE_ALLOW_DECRYPTED_DESTINATION;
-    if (dwMajorVersion > 5) {
+    if (IsVistaOrLater()) {
         bool path1Remote, path2Remote;
         if (!IsRemoteFilePath(filePath.get(), path1Remote) || 
             !IsRemoteFilePath(destPath.get(), path2Remote) ||