//you will need System.IO and System.Diagnostics
//Change the configuration to Debug to see a list of folders that are being read.
//Change to release to see just the folders that cannot be read.
//The search will be faster in Release configuration

      private void Search()
      {
          foreach (String drive in Directory.GetLogicalDrives())
          {
              Debug.WriteLine(drive);
              foreach (DirectoryInfo child in getDirectories(drive))
              {
                  Debug.WriteLine(child.FullName);
                  FindFiles(child);
              }
          }
      }

      private void FindFiles(DirectoryInfo dir)
      {
          try
          {
              DirectoryInfo[] children = getDirectories(dir);
              if (children.Length > 0)
              {
                  foreach (DirectoryInfo child in children)
                  {
                      Debug.WriteLine(child.FullName);
                      FindFiles(child);
                  }
              }
              else
              {
                  FileInfo[] Files = dir.GetFiles("*.txt");
                  if (Files.Length > 0)
                  {
                      //Found some text files.
                      //Do something
                  }
              }
          }
	   catch (Exception ex) {
		System.Console.WriteLine(ex.Message);
          }
      }

      private bool AttrOn(FileAttributes attr, FileAttributes field)
      {
          return (attr & field) == field;
      }

      public DirectoryInfo[] getDirectories(DirectoryInfo dir)
      {
          if (AttrOn(dir.Attributes, FileAttributes.Offline))
          {
              Console.Out.WriteLine(dir.Name + " is not mapped ");
              return new DirectoryInfo[] { };
          }
          if (!dir.Exists)
          {
              Console.Out.WriteLine(dir.Name + " does not exist ");
              return new DirectoryInfo[] { };
          }
          try
          {
              return dir.GetDirectories();
          }
          catch (Exception ex)
          {
              Console.Out.WriteLine(ex.Message);
              Console.Out.WriteLine(ex.StackTrace);
              return new DirectoryInfo[] { };
          }
      }

      public DirectoryInfo[] getDirectories(String strDrive)
      {
          DirectoryInfo dir = new DirectoryInfo(strDrive);
          return getDirectories(dir);
      }