well to start with, I'd look into changing to a later version i.e. 6.06 (aka Dapper) is now the current one, 2 versions newer.
I don't know how to check, but you'd need to find out whether your lappy see's things as a laptop with 2 monitors connected so the graphics device can run things as a "double headed" system or whether it's just a case having to run the install but not actually using the laptops screen so that it's set up only too use (optimise maybe ??) the external monitor.
I know that graphics cards/devices that have 2 outlets can be set up so that they are both usable, but it depends on how your lappy is actually designed to work.
You might also have a look here
- 5.04 aka Hoary.