In ATI's download page, where the 4.12 driver are, there are several options. Read them carefully. You want the driver and the control panel. It is two separate downloads.
Install the driver first, then after the computer reboots, install the control panel.
Of course, remove the current drivers and control panel (if you remove the driver, the control panel is removed at the same time).
I would link to the files you need, but ATI's site no longer allows direct links.