Renaming All Files in a Directory - C#

The following method searches a given directory (dir), and all subdirectories for files. Each file is renamed with a time stamp and an additional tag specified by a user (userADD).

        public static void renameDir(DirectoryInfo dir, string userADD)
        {
            System.DateTime dt = System.DateTime.Now;
            string timeHolder = String.Format("{0:MMddyyyy}", dt);

            DirectoryInfo renamed = new DirectoryInfo(dir.FullName + "\\renamed\\");
            if (!renamed.Exists)
                renamed.Create();


            foreach (FileInfo file in dir.GetFiles())
            {
                string temp = (renamed.FullName + "\\" + file.Name.Substring(0, file.Name.Length - 4) +
                            "_" + userADD +
                            "_" + timeHolder +
                            file.Extension);

                //file.CopyTo(temp);
                File.Move(file.FullName, temp);
                
            }
            foreach (DirectoryInfo subDir in dir.GetDirectories())
            {
                if (!subDir.Name.Equals("renamed"))
                    renameDir(subDir , userADD);
            }
        }