Change resolution to 1440*900 in Ubuntu

Today I've got a new LCD display which is 19 inches. Thus the resolution 1024*768 is no longer suitable for it.
In Windows system it can be detected automatically and you can just choose the 1440*900 resolution solution. However in Ubuntu I had to set by my self.
First execute "sudo dpkg-reconfigure -phigh xserver-xorg" in terminal and a new file "/etc/X11/xorg.conf" while backup the former xorg.conf to "/etc/X11/xorg.conf.date"(mine is /etc/X11/xorg.conf.20080518124841); Second, add 1440*900 to Section "Screen" in /etc/X11/xorg.conf; Then restart the computer; Finally, choose 1440*900 and get the suitable resolution.