Screen resolution problem after ubuntu installation

The live CD detects everything correctly, but after installation the resolution is set to 800x600
and there are no higher options.

This problem and its solutions are well discussed here.

This is the solution that worked:

Launch a Terminal window by going Applications > Terminal
Type this at the command prompt:

sudo gedit /etc/X11/xorg.conf
Find the text:

Section "Monitor"
Create the entries for "HorizSync" and "VertRefresh" each on a separate line with the values corresponding to your monitor.
For example, I have a generic 17 inch monitor at 1024x768 and my section looks like this:

Section "Monitor"
Identifier "HWP" # this is my monitor name
Option "DPMS" # default options, leave these alone
HorizSync 28-60 # horizontal refresh frequencies
VertRefresh 43-60 # vertical refresh frequencies
EndSection
Reboot your computer and your resolution should be all set

The official Ubuntu help for this problem is here.