Dell Inspiron 600/ Radeon 9000 Display Adapter/ Viewsonic Widescreen LCD Monitor

I am trying to get a Viewsonic VX2025sm 20.1" widescreen monitor to display properly as an external monitor with my Dell Inspiron 600 laptop that has a Mobility Radeon 9000 display adapter.  I have loaded the driver for the monitor from Viewsonic.  The monitor should be displaying in 1680 x 1050. However, the choices of resolution I get in display properties in Control Panel are not for a widescreen monitor and so the display is horizontally stretched. For example, I can get 1600x1200.

 

I would appreciate any help in getting this monitor to display properly. Thanks.