Dual monitor for windows xp or windows 7. Laptop as the primary display and an lcd monitor the extension monitor.
Dual screens on laptop is a little harder than a desktop.
First plug in your external screen then right click on your desktop
Click on properties and click the advanced tab. You want to right click on the second monitor and click "attached" and if you want to be able to drag items from one screen to another, set it as you see here:
Click on Screen Resolution, and make sure Multiple displays is set to "Extend these displays" and similar to the picture below.
On either Operating system, if you do not see the dual screen options, it is possible that your graphics card does not allow it.