Problem

using System;
using System.Collections.Generic;
using System.Text;

using System.Diagnostics;
using System.Drawing.Printing;

using Microsoft.Win32;

namespace DefaultPrinterFix
{
    class Program
    {
        public class ToDelete
        {
            public string valname;
            public RegistryKey node;
        }

        static void Main(string[] args)
        {
            Dictionary<string, bool> Printers = new Dictionary<string, bool>();

            foreach (string printer in PrinterSettings.InstalledPrinters)
            {
                Printers[printer.ToLower()] = true;
                Console.WriteLine("Found printer \"{0}\"", printer);
            }

            Console.Write("\n");

            Console.WriteLine("Searching for obsolete printers...");

            LinkedList<ToDelete> Obsolete = new LinkedList<ToDelete>();
            RegistryKey rootnode;

            // Locate first set...
            rootnode = Registry.CurrentUser.OpenSubKey("Software\\Microsoft\\Windows NT\\CurrentVersion\\Devices", true);
            Debug.Assert(rootnode != null, "Could not find the entry for \"Software\\Microsoft\\Windows NT\\CurrentVersion\\Devices\"");

            foreach (string name in rootnode.GetValueNames()) // These are values
            {
                if (!Printers.ContainsKey(name.ToLower()))
                {
                    Console.WriteLine("Found obsolete printer refrence to {0}", name);

                    Obsolete.AddLast(new ToDelete()
                    {
                        valname = name,
                        node = rootnode
                    });
                }
            }

            // Locate second set...
            rootnode = Registry.CurrentUser.OpenSubKey("Printers\\Connections", true);
            Debug.Assert(rootnode != null, "Could not find the entry for \"Printers\\Connections\"");

            foreach (string name in rootnode.GetSubKeyNames()) // This section has folders with binary data about the printer, so lets just remove the whole folder
            {
                if (!Printers.ContainsKey(name.Replace(",", "\\").ToLower()))     /* For some reason, the back slashes are replaced with
                                                                         commas; to fix this so we can check the printer is
                                                                         valid we just replace the comma with a backslash.
                                                                         ,,ddrl1,example -> \\ddrl1\example */
                {
                    Obsolete.AddLast(new ToDelete()
                    {
                        valname = name,
                        node = rootnode
                    });
                }
            }

            // Time to delete them...
            if (Obsolete.Count == 0)
                Console.WriteLine("\nNo obsolete printers found!");
            else
            {
                Console.WriteLine("\nFound {0} enteries:\n", Obsolete.Count);
                foreach (ToDelete obj in Obsolete)
                    Console.WriteLine("{0}\\{1}", obj.node, obj.valname);

                Console.Write("\nAre you sure you want to delete these enteries? (y/n): ");

                string line = Console.ReadLine();
                Console.Write("\n");

                if (line == "y" || line == "Y")
                {
                    foreach (ToDelete key in Obsolete)
                    {
                        try { key.node.DeleteValue(key.valname); }
                        catch { }
                        try { key.node.DeleteSubKeyTree(key.valname); }
                        catch { }
                        Console.WriteLine("Deleted \"{0}\\{1}\"", key.node, key.valname);
                    }

                }
                else
                    Console.WriteLine("Halting.");

            }

            Console.WriteLine("\nPush enter to exit.");
            Console.ReadLine();
        }
    }
}