I've just about given up on this!
I have tried, without success, to get Ubuntu to run in 16:9 mode on my Acer TravelMate 4101.
It has an Intel Mobile 915GM/GMS/910GML chipset.
Firstly, I downloaded 915resolution and made the changes for 1280 X 800 but I could still only run at 1024X7128 max at 24 bit.
I then tried sudo dpkg-reconfigure xserver-xorg, but to no avail.
Not to be deterred, I tried manually changing xorg.conf, but again, to no avail.
Next, I downloaded the KDE Desktop, as I was told it has more user-friendly graphical config tools.
Sure enough, it has. It auto-detected that I had a 16:9 widescreen and that it could operate in 1280X800 @ 24 bit.
I thought, great I'm almost there. But alas, when I re-started X it was even worse! I was now locked into 800X600 resolution.
I would like to be able to change completely over to Linux, but as I need it for CAD and photographic work, the aspect ratio has to be correct.
Is there an answer to this, or should I just admit defeat and go cap in hand back to XP?