it is recommended to uninstall any old driver before installing a new one.
go download driver sweeper. This will help you remove all the old files that add/remove program fail to remove. Run this after you use add/remove program or "program and feature" in win 7. Then run the driver sweeper and select "ATI" and click clean.
http://downloads.guru3d.com/Guru3D--...load-1672.html
And if you want to do it safe, what i do is I usually disable my internet before i restart to install the new driver. This would prevent win7 automatic install the driver you don't want upon restarting. Hope this help.