E6400 and additional screen - moves icons when docking

I have a Lattitude E6400 running XP SP3, and an external monitor 1900x1200 which I use as second screen, attached to the docking station.

Every time I dock it, the resolution of laptop's screen is briefly changed to 640x480 during the docking process.

After second or two the resolution is again normal at 1280x800, but all icons on the desktop are squished in the 640x480 corner, and all applications open have their window resized to fit inside 640x480.

How can I prevent this ?