As reported at http://forums.java.net/jive/thread.jspa?messageID=380404
The following test case fails to display a maximized window on WinXP, jdk6u16:

import java.awt.*;
public class test {
    public static void main(String[] args) {
        Frame f = new Frame();
        f.setExtendedState(f.getExtendedState() | Frame.MAXIMIZED_BOTH);
        f.setResizable(false);
        f.setVisible(true);
    }
}

Either the specification of the setResizable/setExtendedState must be updated to reflect their incompatibility, or the bug should be fixed to allow using both methods at once.