Help - Setting up 2 LCD Monitors to new Dell XPS Desktop

I just bought a DELL Studio XPS and I am trying to setup two monitors to it. I got the ATI Radeon 4850 because it had two DVI ports. What i didnt realize is my old 17" Dell LCD requires me to have the DVI and the VGA connection in or it turns off. I havn't tried yet but i am figuring my new 23" widescreen Dell LCD is going to do the samething(It's supposed to arrive later today via Fedex).

What hardware do I need to make this work. I want my second monitor as an extension, not a mirror. Thanks any help will be appreciated.

If I unplug the DVI or VGA the monitor goes black, which confuses me cause on the ATI site.

"Two independent display controllers
Drive two displays simultaneously with independent resolutions, refresh rates, color controls and video overlays for each display"

yet I have to use the other DVI port to plug in my VGA adapter or I cant use a single LCD monitor.

Perhaps you did not quite have 1 plugged in all the way, so it was never getting a signal? Then when you unplugged the other one, all went black. Like I said, it made no sense. You monitor does not need both cables attached to work.