You have a quite old card. If you go to the AMD page and go through the choices, you land here: http://support.amd.com/en-us/download/desktop/legacy?product=Legacy2&os=Linux%20x86_64
In the bottom, you have:
Description: Automated installer and Display Drivers for Xorg 6.9 to
Xserver 1.12 and Kernel version up to 3.4
So, if you want to use the proprietary AMD drivers, you have to stay with a (very old) version of the kernel and X stack. Chances are that you have a newer kernel (try with
uname -a) and X stack (
dpkg -l xserver-xorg); fglrx drivers do not support this configuration. So you have two possibilities:
use the open-source drivers (should work reasonably well; supported by Ubuntu; this is my personal preference)
downgrade kernel and X stack (but here you'll be on your own --- and will come the time when there will be no security support for that).
Note that this situation come from an AMD decision --- the drivers are their and they decide what to do; probably supporting legacy drivers with newer kernels has become too expensive for them.