DougRenamer.cs

using System;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;

namespace DougRenamer
{
    class Program
    {
        private const string DIRECTORY = @"D:\Deluge\Doug\";

        static void Main(string[] args)
        {
            Directory.GetFiles(DIRECTORY).ToList().ForEach(RenameFile);
        }

        private static void RenameFile(string path)
        {
            var file = path.Substring(DIRECTORY.Length);
            var match = Regex.Match(file, "doug([1-9])([0-9]{2})\\.(.+)").Groups.Select(e => e.Value).ToArray();
            var newFile = $"Doug S0{match[1]}E{match[2]}.{match[3]}";
            Console.WriteLine($"Before: {path}");
            Console.WriteLine($"After:  {DIRECTORY + newFile}");
            Console.WriteLine();
            File.Move(path, DIRECTORY + newFile);
        }
    }
}