diff --git a/src/org/ntlab/deltaViewer/MagnetRONMenuBar.java b/src/org/ntlab/deltaViewer/MagnetRONMenuBar.java
index a1a4dc3..0f0dc34 100644
--- a/src/org/ntlab/deltaViewer/MagnetRONMenuBar.java
+++ b/src/org/ntlab/deltaViewer/MagnetRONMenuBar.java
@@ -5,6 +5,7 @@
 import java.util.Locale;
 import java.util.Properties;
 
+import javax.swing.ButtonGroup;
 import javax.swing.JCheckBox;
 import javax.swing.JMenu;
 import javax.swing.JMenuBar;
@@ -64,10 +65,13 @@
 		JMenu animationSettingMenu = add(new JMenu(properties.getProperty("anim_settings")));
 		JCheckBox defaultCheck = new JCheckBox(properties.getProperty("normal"), true);
 		defaultCheck.addActionListener(new ZoomActualAction(magnetRON.getViewer()));
-		defaultCheck.setEnabled(false);
-		animationSettingMenu.add(defaultCheck);
 		JCheckBox autoTrackingCheck = new JCheckBox(properties.getProperty("auto_tracking"), false);
 		autoTrackingCheck.addChangeListener(new AutoTrackingAction(magnetRON.getViewer()));
+		
+		ButtonGroup checkBoxGroup = new ButtonGroup();
+		checkBoxGroup.add(defaultCheck);
+		checkBoxGroup.add(autoTrackingCheck);
+		animationSettingMenu.add(defaultCheck);
 		animationSettingMenu.add(autoTrackingCheck);
 
 		JMenu viewMenu = add(new JMenu(properties.getProperty("view")));