Comment 1 for bug 523749

I gave up and in order to get the right resolution with the original 19 inch screen I had to:
sudo apt-get purge xorg-driver-sisimedia
and
 sudo gdebi Downloads/xorg-driver-sisimedia_0.9-1_i386.deb

Maybe this action combined with other actions would solve the problem but I have up.
see
Question #101553 : Questions : “xserver-xorg-video-sis” package : Ubuntu (24 February 2010)
 https://answers.launchpad.net/ubuntu/+source/xserver-xorg-video-sis/+question/101553