connecting a flat panel second monitor to my Dell PC

I have tried to connect two monitors to my Dell Dimension 8300, but I have found that only one of them is receiving a signal.  I have used the analogue and digital outputs from my G-Force 64mb graphics card and connected a cable from each one of these ports to each monitor, but the monitor connected to the analogue output remains in standby mode and does not come on.  I can only get one monitor to work at any time but not both at the same time. 

Do I need a new graphics card driver to make this work or is there a setting on Windows XP to make both montors work at the same time?  I am using two standard Dell flat panel screens which both accept digital as well as analogue inputs.  One screen is a 19 inch and the other is a 15 inch.  I am using Windows XP home edition.

Can anyone solve this for me?