Multiple Monitors

Ok so I have a ATI Radeon 9800 XT Pro 256mb graphics card. It has an RGB and a DVI port on it, and I have a 20" plugged into the RGB and a 15" plugged into the DVI.

Can I get my desktop to spread across both of them? What can I actually get to display on the 15", at the moment, it just shows my desktop image (no icons or anything) while the 20" just shows what it would normally.

I played around with the settings a bit but didn’t find a way to spread it across or display something different on each monitor.

Edit: I managed to get it so that the cursor pans across both screens (when I move it off the edge of the 20", it apperas on the 15", but I can’t get anything on the 15" except the desktop (all I can do is right click on it, theres no icons, no taskbar, nothing!)