Radeon cant extend desktop dual monitor

I have a new dual monitor display on my ATI Radeon 9250 but all I can achieve at the moment is to have the primary display cloned on the seond monitor. (I have the main monitor plugged in to the VGA and the second monitor in the DVI)
If I click on the Identify button both monitors display the 1 on the screen.
I have checked the box on the second monitor to say extend my desktop onto this display, but it still doesnt do anything.
If I drag my mouse over to the edge of the screen the mouse will continue to move as if there is a second display setup, I just cant get get it to display on the second monitor.
Please help! I have written to ATI to no avail.