diff --git a/src/com/bytezone/diskbrowser/duplicates/CheckBoxActionListener.java b/src/com/bytezone/diskbrowser/duplicates/CheckBoxActionListener.java
new file mode 100644
index 0000000..6d66b4e
--- /dev/null
+++ b/src/com/bytezone/diskbrowser/duplicates/CheckBoxActionListener.java
@@ -0,0 +1,36 @@
+package com.bytezone.diskbrowser.duplicates;
+
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.util.List;
+
+import javax.swing.JButton;
+import javax.swing.JCheckBox;
+
+class CheckBoxActionListener implements ActionListener
+{
+  DiskDetails diskDetails;
+  List<DiskDetails> disksSelected;
+  JButton deleteButton;
+  JButton clearButton;
+
+  public CheckBoxActionListener (DiskDetails diskDetails, List<DiskDetails> disksSelected,
+      JButton deleteButton, JButton clearButton)
+  {
+    this.diskDetails = diskDetails;
+    this.disksSelected = disksSelected;
+    this.deleteButton = deleteButton;
+    this.clearButton = clearButton;
+  }
+
+  @Override
+  public void actionPerformed (ActionEvent e)
+  {
+    if (((JCheckBox) e.getSource ()).isSelected ())
+      disksSelected.add (diskDetails);
+    else
+      disksSelected.remove (diskDetails);
+    deleteButton.setEnabled (disksSelected.size () > 0);
+    clearButton.setEnabled (disksSelected.size () > 0);
+  }
+}
\ No newline at end of file
diff --git a/src/com/bytezone/diskbrowser/duplicates/DuplicatePanel.java b/src/com/bytezone/diskbrowser/duplicates/DuplicatePanel.java
new file mode 100644
index 0000000..4c5501f
--- /dev/null
+++ b/src/com/bytezone/diskbrowser/duplicates/DuplicatePanel.java
@@ -0,0 +1,50 @@
+package com.bytezone.diskbrowser.duplicates;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import javax.swing.JButton;
+import javax.swing.JCheckBox;
+import javax.swing.JLabel;
+import javax.swing.JPanel;
+import javax.swing.SpringLayout;
+
+import com.bytezone.input.SpringUtilities;
+
+public class DuplicatePanel extends JPanel
+{
+  List<JCheckBox> checkBoxes = new ArrayList<JCheckBox> ();
+  List<DiskDetails> duplicateDisks;
+
+  public DuplicatePanel (List<DiskDetails> duplicateDisks, int folderNameLength,
+      List<DiskDetails> disksSelected, JButton deleteButton, JButton clearButton)
+  {
+    this.duplicateDisks = duplicateDisks;
+    setLayout (new SpringLayout ());
+    setAlignmentX (LEFT_ALIGNMENT);
+
+    int count = 0;
+    for (DiskDetails dd : duplicateDisks)
+    {
+      JCheckBox cb = new JCheckBox ();
+      checkBoxes.add (cb);
+
+      cb.addActionListener (
+          new CheckBoxActionListener (dd, disksSelected, deleteButton, clearButton));
+      add (cb);
+      if (++count == 1)
+        add (new JLabel ("Source disk"));
+      else
+      {
+        String text = dd.isDuplicate () ? "Duplicate" : "OK";
+        add (new JLabel (text));
+      }
+      String checksum = dd.isDuplicate () || count == 1 ? ""
+          : " (checksum = " + dd.getChecksum () + ")";
+      add (new JLabel (dd.getAbsolutePath ().substring (folderNameLength) + checksum));
+    }
+    SpringUtilities.makeCompactGrid (this, duplicateDisks.size (), 3, //rows, cols
+        10, 0, //initX, initY
+        10, 0); //xPad, yPad
+  }
+}
\ No newline at end of file
diff --git a/src/com/bytezone/diskbrowser/duplicates/DuplicateWindow.java b/src/com/bytezone/diskbrowser/duplicates/DuplicateWindow.java
new file mode 100644
index 0000000..4bbbf0c
--- /dev/null
+++ b/src/com/bytezone/diskbrowser/duplicates/DuplicateWindow.java
@@ -0,0 +1,162 @@
+package com.bytezone.diskbrowser.duplicates;
+
+import java.awt.BorderLayout;
+import java.awt.Dimension;
+import java.awt.event.ActionEvent;
+import java.awt.event.ActionListener;
+import java.io.File;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.Map;
+
+import javax.swing.*;
+
+public class DuplicateWindow extends JFrame
+{
+  int unfinishedWorkers;
+  int folderNameLength;
+  Map<String, List<DiskDetails>> duplicateDisks;
+  File rootFolder;
+
+  JButton buttonDelete = new JButton ("Delete selected");
+  JButton buttonCancel = new JButton ("Cancel");
+  JButton buttonAll = new JButton ("Select all duplicates");
+  JButton buttonClear = new JButton ("Clear all");
+  JPanel mainPanel = new JPanel ();
+
+  List<DiskDetails> disksSelected = new ArrayList<DiskDetails> ();
+  List<DuplicatePanel> duplicatePanels = new ArrayList<DuplicatePanel> ();
+
+  public DuplicateWindow (File rootFolder)
+  {
+    super ("Duplicate Disk Detection - " + rootFolder.getAbsolutePath ());
+
+    unfinishedWorkers = duplicateDisks.size ();
+    folderNameLength = rootFolder.getAbsolutePath ().length ();
+
+    mainPanel.setLayout (new BoxLayout (mainPanel, BoxLayout.PAGE_AXIS));
+
+    JScrollPane sp =
+        new JScrollPane (mainPanel, ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS,
+            ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER);
+    sp.getVerticalScrollBar ().setUnitIncrement (100);
+    add (sp, BorderLayout.CENTER);
+
+    JPanel panel = new JPanel ();
+    panel.add (buttonClear);
+    panel.add (buttonAll);
+    panel.add (buttonDelete);
+    panel.add (buttonCancel);
+    add (panel, BorderLayout.SOUTH);
+
+    buttonClear.setEnabled (false);
+    buttonAll.setEnabled (false);
+    buttonDelete.setEnabled (false);
+    buttonCancel.setEnabled (false);
+
+    buttonAll.addActionListener (new ActionListener ()
+    {
+      @Override
+      public void actionPerformed (ActionEvent e)
+      {
+        for (DuplicatePanel dp : duplicatePanels)
+        {
+          int count = 0;
+          for (JCheckBox cb : dp.checkBoxes)
+          {
+            if (count > 0 && dp.duplicateDisks.get (count).isDuplicate ())
+              if (!cb.isSelected ())
+              {
+                cb.setSelected (true); // doesn't fire the actionListener!
+                disksSelected.add (dp.duplicateDisks.get (count));
+              }
+            ++count;
+          }
+        }
+        buttonDelete.setEnabled (disksSelected.size () > 0);
+        buttonClear.setEnabled (disksSelected.size () > 0);
+      }
+    });
+
+    buttonClear.addActionListener (new ActionListener ()
+    {
+      @Override
+      public void actionPerformed (ActionEvent e)
+      {
+        for (DuplicatePanel dp : duplicatePanels)
+          for (JCheckBox cb : dp.checkBoxes)
+            cb.setSelected (false); // doesn't fire the actionListener!
+        disksSelected.clear ();
+        buttonDelete.setEnabled (false);
+        buttonClear.setEnabled (false);
+      }
+    });
+
+    buttonCancel.addActionListener (new ActionListener ()
+    {
+      @Override
+      public void actionPerformed (ActionEvent e)
+      {
+        DuplicateWindow.this.setVisible (false);
+      }
+    });
+
+    buttonDelete.addActionListener (new ActionListener ()
+    {
+      @Override
+      public void actionPerformed (ActionEvent e)
+      {
+        int totalDeleted = 0;
+        int totalFailed = 0;
+        for (DuplicatePanel dp : duplicatePanels)
+        {
+          int count = 0;
+          for (JCheckBox cb : dp.checkBoxes)
+          {
+            if (cb.isSelected () && false)
+            {
+              DiskDetails dd = dp.duplicateDisks.get (count);
+              if (dd.delete ())
+              {
+                ++totalDeleted;
+                System.out.println ("Deleted : " + dd);
+              }
+              else
+              {
+                ++totalFailed;
+                System.out.println ("Failed  : " + dd);
+              }
+            }
+            ++count;
+          }
+        }
+        System.out.printf ("Deleted : %d, Failed : %d%n", totalDeleted, totalFailed);
+      }
+    });
+
+    setSize (600, 700);
+    setLocationRelativeTo (null);
+    setDefaultCloseOperation (HIDE_ON_CLOSE);
+    setVisible (true);
+  }
+
+  // create a DuplicatePanel based on the updated DiskDetails
+  public synchronized void addResult (List<DiskDetails> duplicateDisks)
+  {
+    // create panel and add it to the window
+    DuplicatePanel dp = new DuplicatePanel (duplicateDisks, folderNameLength,
+        disksSelected, buttonDelete, buttonClear);
+    mainPanel.add (dp);
+    duplicatePanels.add (dp);
+
+    validate ();
+
+    if (--unfinishedWorkers == 0)
+    {
+      buttonAll.setEnabled (true);
+      buttonCancel.setEnabled (true);
+    }
+    else
+      mainPanel.add (Box.createRigidArea (new Dimension (0, 20)));
+  }
+}
diff --git a/src/com/bytezone/diskbrowser/duplicates/DuplicateWorker.java b/src/com/bytezone/diskbrowser/duplicates/DuplicateWorker.java
new file mode 100644
index 0000000..c151cd8
--- /dev/null
+++ b/src/com/bytezone/diskbrowser/duplicates/DuplicateWorker.java
@@ -0,0 +1,44 @@
+package com.bytezone.diskbrowser.duplicates;
+
+import java.util.List;
+
+import javax.swing.SwingWorker;
+
+public class DuplicateWorker extends SwingWorker<List<DiskDetails>, Void>
+{
+  List<DiskDetails> duplicateDisks;
+  DuplicateWindow owner;
+
+  public DuplicateWorker (List<DiskDetails> duplicateDisks, DuplicateWindow owner)
+  {
+    this.duplicateDisks = duplicateDisks;
+    this.owner = owner;
+  }
+
+  @Override
+  protected void done ()
+  {
+    try
+    {
+      owner.addResult (get ());
+    }
+    catch (Exception e)
+    {
+      e.printStackTrace ();
+    }
+  }
+
+  @Override
+  protected List<DiskDetails> doInBackground () throws Exception
+  {
+    long firstChecksum = -1;
+    for (DiskDetails dd : duplicateDisks)
+    {
+      if (firstChecksum < 0)
+        firstChecksum = dd.getChecksum ();
+      else
+        dd.setDuplicate (dd.getChecksum () == firstChecksum);
+    }
+    return duplicateDisks;
+  }
+}
\ No newline at end of file
diff --git a/src/com/bytezone/diskbrowser/gui/DuplicateAction.java b/src/com/bytezone/diskbrowser/gui/DuplicateAction.java
index a8c298a..4ed8319 100644
--- a/src/com/bytezone/diskbrowser/gui/DuplicateAction.java
+++ b/src/com/bytezone/diskbrowser/gui/DuplicateAction.java
@@ -1,23 +1,17 @@
 package com.bytezone.diskbrowser.gui;
 
-import static javax.swing.ScrollPaneConstants.HORIZONTAL_SCROLLBAR_NEVER;
-import static javax.swing.ScrollPaneConstants.VERTICAL_SCROLLBAR_ALWAYS;
-
-import java.awt.BorderLayout;
-import java.awt.Dimension;
 import java.awt.event.ActionEvent;
-import java.awt.event.ActionListener;
 import java.io.File;
-import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
 
-import javax.swing.*;
+import javax.swing.Action;
 
 import com.bytezone.common.DefaultAction;
 import com.bytezone.diskbrowser.duplicates.DiskDetails;
+import com.bytezone.diskbrowser.duplicates.DuplicateWindow;
+import com.bytezone.diskbrowser.duplicates.DuplicateWorker;
 import com.bytezone.diskbrowser.gui.RootDirectoryAction.RootDirectoryListener;
-import com.bytezone.input.SpringUtilities;
 
 public class DuplicateAction extends DefaultAction implements RootDirectoryListener
 {
@@ -64,260 +58,8 @@ public class DuplicateAction extends DefaultAction implements RootDirectoryListe
       window.setVisible (true);
       return;
     }
-    window = new DuplicateWindow ();
+    window = new DuplicateWindow (rootFolder);
     for (List<DiskDetails> diskList : duplicateDisks.values ())
       new DuplicateWorker (diskList, window).execute ();
   }
-
-  class DuplicateWindow extends JFrame
-  {
-    int unfinishedWorkers;
-    int folderNameLength;
-
-    JButton buttonDelete = new JButton ("Delete selected");
-    JButton buttonCancel = new JButton ("Cancel");
-    JButton buttonAll = new JButton ("Select all duplicates");
-    JButton buttonClear = new JButton ("Clear all");
-    JPanel mainPanel = new JPanel ();
-
-    List<DiskDetails> disksSelected = new ArrayList<DiskDetails> ();
-    List<DuplicatePanel> duplicatePanels =
-        new ArrayList<DuplicateAction.DuplicatePanel> ();
-
-    public DuplicateWindow ()
-    {
-      super ("Duplicate Disk Detection - " + rootFolder.getAbsolutePath ());
-      unfinishedWorkers = duplicateDisks.size ();
-      folderNameLength = rootFolder.getAbsolutePath ().length ();
-
-      mainPanel.setLayout (new BoxLayout (mainPanel, BoxLayout.PAGE_AXIS));
-
-      JScrollPane sp = new JScrollPane (mainPanel, VERTICAL_SCROLLBAR_ALWAYS,
-          HORIZONTAL_SCROLLBAR_NEVER);
-      sp.getVerticalScrollBar ().setUnitIncrement (100);
-      add (sp, BorderLayout.CENTER);
-
-      JPanel panel = new JPanel ();
-      panel.add (buttonClear);
-      panel.add (buttonAll);
-      panel.add (buttonDelete);
-      panel.add (buttonCancel);
-      add (panel, BorderLayout.SOUTH);
-
-      buttonClear.setEnabled (false);
-      buttonAll.setEnabled (false);
-      buttonDelete.setEnabled (false);
-      buttonCancel.setEnabled (false);
-
-      buttonAll.addActionListener (new ActionListener ()
-      {
-        @Override
-        public void actionPerformed (ActionEvent e)
-        {
-          for (DuplicatePanel dp : duplicatePanels)
-          {
-            int count = 0;
-            for (JCheckBox cb : dp.checkBoxes)
-            {
-              if (count > 0 && dp.duplicateDisks.get (count).isDuplicate ())
-                if (!cb.isSelected ())
-                {
-                  cb.setSelected (true); // doesn't fire the actionListener!
-                  disksSelected.add (dp.duplicateDisks.get (count));
-                }
-              ++count;
-            }
-          }
-          buttonDelete.setEnabled (disksSelected.size () > 0);
-          buttonClear.setEnabled (disksSelected.size () > 0);
-        }
-      });
-
-      buttonClear.addActionListener (new ActionListener ()
-      {
-        @Override
-        public void actionPerformed (ActionEvent e)
-        {
-          for (DuplicatePanel dp : duplicatePanels)
-            for (JCheckBox cb : dp.checkBoxes)
-              cb.setSelected (false); // doesn't fire the actionListener!
-          disksSelected.clear ();
-          buttonDelete.setEnabled (false);
-          buttonClear.setEnabled (false);
-        }
-      });
-
-      buttonCancel.addActionListener (new ActionListener ()
-      {
-        @Override
-        public void actionPerformed (ActionEvent e)
-        {
-          DuplicateWindow.this.setVisible (false);
-        }
-      });
-
-      buttonDelete.addActionListener (new ActionListener ()
-      {
-        @Override
-        public void actionPerformed (ActionEvent e)
-        {
-          int totalDeleted = 0;
-          int totalFailed = 0;
-          for (DuplicatePanel dp : duplicatePanels)
-          {
-            int count = 0;
-            for (JCheckBox cb : dp.checkBoxes)
-            {
-              if (cb.isSelected () && false)
-              {
-                DiskDetails dd = dp.duplicateDisks.get (count);
-                if (dd.delete ())
-                {
-                  ++totalDeleted;
-                  System.out.println ("Deleted : " + dd);
-                }
-                else
-                {
-                  ++totalFailed;
-                  System.out.println ("Failed  : " + dd);
-                }
-              }
-              ++count;
-            }
-          }
-          System.out.printf ("Deleted : %d, Failed : %d%n", totalDeleted, totalFailed);
-        }
-      });
-
-      setSize (600, 700);
-      setLocationRelativeTo (null);
-      setDefaultCloseOperation (HIDE_ON_CLOSE);
-      setVisible (true);
-    }
-
-    // create a DuplicatePanel based on the updated DiskDetails
-    public synchronized void addResult (List<DiskDetails> duplicateDisks)
-    {
-      // create panel and add it to the window
-      DuplicatePanel dp = new DuplicatePanel (duplicateDisks, folderNameLength,
-          disksSelected, buttonDelete, buttonClear);
-      mainPanel.add (dp);
-      duplicatePanels.add (dp);
-
-      validate ();
-
-      if (--unfinishedWorkers == 0)
-      {
-        buttonAll.setEnabled (true);
-        buttonCancel.setEnabled (true);
-      }
-      else
-        mainPanel.add (Box.createRigidArea (new Dimension (0, 20)));
-    }
-  }
-
-  class DuplicatePanel extends JPanel
-  {
-    List<JCheckBox> checkBoxes = new ArrayList<JCheckBox> ();
-    List<DiskDetails> duplicateDisks;
-
-    public DuplicatePanel (List<DiskDetails> duplicateDisks, int folderNameLength,
-        List<DiskDetails> disksSelected, JButton deleteButton, JButton clearButton)
-    {
-      this.duplicateDisks = duplicateDisks;
-      setLayout (new SpringLayout ());
-      setAlignmentX (LEFT_ALIGNMENT);
-
-      int count = 0;
-      for (DiskDetails dd : duplicateDisks)
-      {
-        JCheckBox cb = new JCheckBox ();
-        checkBoxes.add (cb);
-
-        cb.addActionListener (
-            new CheckBoxActionListener (dd, disksSelected, deleteButton, clearButton));
-        add (cb);
-        if (++count == 1)
-          add (new JLabel ("Source disk"));
-        else
-        {
-          String text = dd.isDuplicate () ? "Duplicate" : "OK";
-          add (new JLabel (text));
-        }
-        String checksum = dd.isDuplicate () || count == 1 ? ""
-            : " (checksum = " + dd.getChecksum () + ")";
-        add (new JLabel (dd.getAbsolutePath ().substring (folderNameLength) + checksum));
-      }
-      SpringUtilities.makeCompactGrid (this, duplicateDisks.size (), 3, //rows, cols
-          10, 0, //initX, initY
-          10, 0); //xPad, yPad
-    }
-  }
-
-  class CheckBoxActionListener implements ActionListener
-  {
-    DiskDetails diskDetails;
-    List<DiskDetails> disksSelected;
-    JButton deleteButton;
-    JButton clearButton;
-
-    public CheckBoxActionListener (DiskDetails diskDetails,
-        List<DiskDetails> disksSelected, JButton deleteButton, JButton clearButton)
-    {
-      this.diskDetails = diskDetails;
-      this.disksSelected = disksSelected;
-      this.deleteButton = deleteButton;
-      this.clearButton = clearButton;
-    }
-
-    @Override
-    public void actionPerformed (ActionEvent e)
-    {
-      if (((JCheckBox) e.getSource ()).isSelected ())
-        disksSelected.add (diskDetails);
-      else
-        disksSelected.remove (diskDetails);
-      deleteButton.setEnabled (disksSelected.size () > 0);
-      clearButton.setEnabled (disksSelected.size () > 0);
-    }
-  }
-
-  class DuplicateWorker extends SwingWorker<List<DiskDetails>, Void>
-  {
-    List<DiskDetails> duplicateDisks;
-    DuplicateWindow owner;
-
-    public DuplicateWorker (List<DiskDetails> duplicateDisks, DuplicateWindow owner)
-    {
-      this.duplicateDisks = duplicateDisks;
-      this.owner = owner;
-    }
-
-    @Override
-    protected void done ()
-    {
-      try
-      {
-        owner.addResult (get ());
-      }
-      catch (Exception e)
-      {
-        e.printStackTrace ();
-      }
-    }
-
-    @Override
-    protected List<DiskDetails> doInBackground () throws Exception
-    {
-      long firstChecksum = -1;
-      for (DiskDetails dd : duplicateDisks)
-      {
-        if (firstChecksum < 0)
-          firstChecksum = dd.getChecksum ();
-        else
-          dd.setDuplicate (dd.getChecksum () == firstChecksum);
-      }
-      return duplicateDisks;
-    }
-  }
 }
\ No newline at end of file