Do you have it installed on the machine in your signature?
Are you trying to run the install CD or have you completed the install?
If you are trying to run the CD to install then please try the text based installer:
32bit text based installer
64bit text based installer
If you have completed the install and are trying to run Ubuntu then:
Boot your machine.
When it says starting grub and gives the countown, hit ESC
Choose the option that says (single user mode)
When it's finished booting you will be at a command prompt.
Type this and make a note of it.
Now type this:
Code:
sudo apt-get install xorg-driver-fglrx
Enter your password when prompted - it will appear as though you are not typing, don't worry this is normal)
Once that has finished downloading and installing, type this:
Code:
sudo apt-get install linux-restricted-modules-(uname -r)
Where (uname -r) is, add the result you got from typing that command in earlier - without the brackets.
Once that has downloaded and installed, type this:
Code:
sudo dpkg-reconfigure xserver-xorg
You will need to select the fglrx driver.
Once that is all done, just press CTRL ALT DEL to reboot.
Hopefully you will now be able to login!
If not then please post on
http://www.ubuntuforums.org with the steps I have asked you to take above.