Achieving Windows XP "look"

The above image shows my problem. When I create a GUI in netbeans, the preview of the GUI does not match the actual GUI shown when running in two ways. One (in a minor sense) is that it does not have the windows xp look for its buttons, borders and such. Two, (more importantly) is that it does not maintain the dimensions I give it. Notice how the bottom jpanel "grows" horizontally when I run the program?

Is this fixable/preventable?