Ok I would go into the control panel and uninstall any entrys to the ati drivers there if there are any.
Then i'd open up the device manager and remove my graphics card from the list and restart(uninstall it). Then when windows restarts it will come up with found new hardware installing drivers. It will probably install it as a standard vga graphics card. Once this is complete I'd then open up device mananger update drivers and then update them using your disk