ALWAYS uninstall old drivers, especially for ATI cards. Nvidia can be more unforgiving as it will uninstall the old before installing the new, but ATI doesn't.
Uninstall through Add/Remove, boot the safe mode, use Driver Sweeper, boot back into Windows, install the new drivers. Yes it is a pain, but it ensures you won't have any problems.
Uninstall through Add/Remove, boot the safe mode, use Driver Sweeper, boot back into Windows, install the new drivers. Yes it is a pain, but it ensures you won't have any problems.