el ner beans no tiene nada que ber
lo que Debes hacer es meter un escritorio dentro de un frame y luego meterle varias ventanitas
package project1;
import java.awt.BorderLayout;
import java.awt.Color;
import java.awt.Dimension;
import java.awt.Rectangle;
import javax.swing.JDesktopPane;
import javax.swing.JFrame;
import javax.swing.JInternalFrame;
public class Frame1 extends JFrame{
BorderLayout borderLayout1=new BorderLayout();
JDesktopPane jDesktopPane1=new JDesktopPane();
JInternalFrame jif1=new JInternalFrame();
JInternalFrame jif2=new JInternalFrame();
public Frame1(){
try{
jbInit();
}
catch(Exception e){
e.printStackTrace();
}
}
private void jbInit() throws Exception{
this.getContentPane().setLayout(borderLayout1);
this.setSize( new Dimension(400, 300) );
jDesktopPane1.setBackground(Color.white);
jif1.setBounds(new Rectangle(0,0,140,110));
jif2.setBounds(new Rectangle(90,45,205,125));
jif1.show();
jif2.show();
jDesktopPane1.add(jif2,null);
jDesktopPane1.add(jif1,null);
this.getContentPane().add(jDesktopPane1,BorderLayout.CENTER);
}
}