Newer Video cards do not usually have 2 vga ports. You cannot use the second builtin video port that is normally behind the snap on cap. That is only for computers without a stand alone video card. Your video card has to have 2 outputs--usually dvi and vga or 2 dvi. Post your model video card or look up the stats at the ATI website. Look up dual monitors in Vista Help to see how to activate dual monitors if your card has 2 ports.
I recently got my Inspiron and trying to set up a second monitor on it.It was supplied with two VGA ports. One has my main monitor the other a secondary one. My main works fine, however my secondary one just says no input. Is there something wrong with the second VGA port? Neither Vista or Catalyst control centre cannot detect the monitor either.