Need Help Configuring Secondary Display

[Ragnar35]

I am having trouble setting up my laptop's secondary display. Here is what I have done so far:

1. I own a 1 year old Dell Inspiron 8600 w/ GeForce FX Go5200 graphics card, Windows XP Home.
2. I have gone into the display settings, and attempted to check the box that says "Extend my Windows Desktop Onto This Monitor" Each time I hit "Apply", the check mark is deleted from the check box.

I have tried to follow the instructions in the manual, without any luck. Any suggestions?

Thanks!
Paul