Did the installation process complete? It is normal for the screen to flash and go off a few times during the installation of graphics drivers.
If in doubt, go to the Control Panel and uninstall all Catalyst software, then try again.
Thankyou, I'll let you know- yes it did flash and it definitely finished. Basically when I uninstalled the drivers and rebooted the ratio was sorted- so I can tell it is a driver problem. On that note, is there any way to download older drivers?