Video out to LCD

[Jim]

Dell Laptop , kubuntu-7.10 .

If  I do a Fn-F8 on my laptop , to a external LCD at 1024x768, the 
display is off to the left and not centered on Ext LCD.
Can't get ext LCD monitor to center desktop.
If I Fn-F8 again and bring display back to laptop the display is at a 
very low resolution and spreads off both sides of laptops lcd display.
Have to restart X to get back to normal.
I have Fedora 8 on this Laptop and have no problems displaying to ext. LCD.
What settings do I change to get Kubuntu to work ?