For some reason, Mouse nuked my response to this. Since you're are upgrading from one ATI to another, you shouldn't need to run driver sweeper. You shouldn't run into any problems at all.
One item of note, however. I wouldn't use the drivers found on the CD. They are generally out of date. Download the latest drivers directly from http://ati.amd.com
and save them to your hard drive.
Install the new graphics card and then boot up your system. Then install the downloaded drivers.