title: How to make "Open File..." window in netbeans PLATFORM?
body: <p>I need to create something like internal frame in netbeans <em>platform</em>, which loads file from any location.
  I tried it by jInternalFrame, but I was not able to find some container to which I can add my frame. I am working in netbeans <strong>platform</strong>, which has own pre-created main window.</p>
  
  <p>Pease help me by any advice, I am dealing with this about 10 hours, still without result.</p>