DVI port on docking station

[Specter]

I visited a second hand store recently and found a docking station for the T4x (and others). It was a dollar and a half, so I had to buy it and give it a try. I thought it would be broken, but in fact it wasn't.

I have tried to use a 20" screen connected to the DVI-port of the dock, but I cannot get my computer/dock to drive the screens full 1600x1200 resolution. The choice of 1600x1200 in "Display Properties" in Windows is there and I can choose this, but the screen shows something more like 1280x1024.

Will the docking station or my ThinkPad T41 not handle 1600x1200 resolution or am I missing something?