Dell video drivers problems

I have a Dell Inspiron 1150 which has just been fitted with a new motherboard. When I got it back it booted with the video display at about half size, centered in the screen and with a black border around it. I reinstalled Windows and updated all the drivers via Device Manager and it runs Windows full size, no problem.
However the problem of it booting with half size screens persists. This means that when I run Ubuntu from a CD, that is half size too, centered in the middle of the screen. I've scoured the Dell's BIOS. I've adjusted the UMA size to 8MB (for the integrated video) and that doesn't make any difference. I can find nothing else related in the BIOS.
Someone in other forums had a similar problem, which was resolved by pressing 'fn' and 'F7' during boot. That doesn't help.
I have gone to Dell’s website and downloaded all the available video drivers for the Inspiron 1150. The files are: R78792.exe; R80551.exe and R105909.exe. The messages I get when I try to install these drivers are:

The INF file does not contain information for this system hardware. Setup will abort.
The system does not meet the minimum requirements for installing the software. Setup will exit.

I would warmly appreciate any suggestions or comments on this.

Stephen.