oh I thought you meant you only had two VGA plugs... then the answer is simple, buy a better graphics card you cheap bugger!
You still on an ancient AGP card i take it? You can only output one image to one port, if you want dual monitors you must have two outputs, on the same card on on two different cards that will play nicely together.
Any card made over the last several years, barring the extreme budget ones have at least 1 VGA and 1 DVI output, all modern cards will have 2x DVI output for HD or for dual monitors.
You need a better or another graphics card to use dual monitor. If its got tv out you maybe able to have tv-out + VGA to different desktops though.