Welcome to DriverHeaven
Here is what I would try.
1: Go to add/remove programs and remove all ati software, MMC, Control Panel, Drivers etc.
2:Boot your system into "Safe Mode"
3:Run Driver Cleaner and remove all traces of ATi, then while not necessary you may also want to run the Cab cleaner as well
4:Reboot let Windows load default driver
5: Do a fresh install of your new video card drivers, and your motherboard chipset drivers and perhaps even directX
Driver Cleaner