When the forms are displayed in the editor they inherit the NetBeans Look and Feel. However when they are run standalone they most likely use the Java default Look and Feel. In order to tell the app to use the platform's default L&F execute the following code before showing any of the frames:
try {
UIManager.setLookAndFeel(
UIManager.getSystemLookAndFeelClassName());
} catch (Exception e) { }
The following link may also be of interest: http://java.sun.com/docs/books/tutorial/uiswing/misc/plaf.html