First of all,do a clean install of a new driver.here is how
1_Download and install "Driver sweeper" from Guru3d.com and install
2_Go to add/remove programs and uninstall the driver and reboot
3_Boot to safe mode and open driver sweeper,then click on ATI and then click on clean
4_Reboot and boot normally to windows and install the latest VGA driver. after that,reboot and its done.