After installing Ubuntu 12.04LTS I tried to change my screen resolution from 640 by 480 to the one suitable for my system but discovered that I cannot. I tried xrandr but it did not work out. Please what can I do to get the best resolution for my system. The resolution I use on windows is 1280 by 800. How can I get same on Ubuntu or something close to that as the maximum resolution on my linux is the 640 by 480?
Go to the top left (in unity) and search for 'additional drivers'. Install the recommended or proprietary drivers. You might have to reboot. If this doesn't work, add a comment on this answer and I'll try again.