Well, the best you could do is make sure you completely uninstall your current videocard drivers using this tool:
http://www.themightyatom.nl/stuff/cat-uninstaller.zipIts an official tool from ATI, so its save to use, i just host a copy on my website for backup purpose.
So get that, uninstall the driver, reboot, download and install the latest driver package from the ATI website, reboot.
Now you are sure that you have a clean installation of the videocard drivers with no traces of left behind drivers.
Hope this helps. I use the uninstaller everytime i install a new driver. Works fine.