Optiplex 745 with Radeon X1300 Pro card and SP2208WFP

I run four computers through a KVM switch so I can share a single keyboard, mouse and monitor.  I just recently replaced my current monitor with a Consumer Performance 22W (SP2208WFP) from Dell.  All the PCs are running XP Pro except the newer one which is running Vista.  As the KVM box is older and uses PS/2 and VGA ports (not ready to spend the money to go to a USB compatible switch) I have the flat panel connected to the switch via a VGA cable.  Each computer is hooked up with a VGA cable and in 1-2 cases a DVI adapter is required. 

The native resolution for the monitor is 1680 X 1050.  All the computers seems to handle this arrangement fine except the Dell Optiplex 745 which has a 256MB Radeon X1300 Pro graphics card.  When I set the resolution on this one to the recommended resolution for the monitor, I see shadows around desktop icons and blurriness.  I believe the card has a DVI adpater that splits into two VGA connectors as if it would support dual monitors.  I also noticed that XP does not allow me to crank the resolution to the recommended setting directly, I have to run the ATI desktop tool provided with the graphics card to set it that high.

Am I missing something?  Is there a setting or a driver upgrade that might correct the problem.  I'm considering getting rid of the adapter for a straight DVI-VGA adapter instead of the splitter that's there now.