It is required to configure the advanced settings of your card to take the most advantage of it. It adds an icon to the systray for quick access to some settings. I don't remember details because I replaced my ATI All In Wonder for a 6600GT and an ATI HDTV adapter.
You don't need to install the Multimedia Center, I never liked it except that I needed it to watch TV with the ATI All In Wonder.
From ATI's website about
Catalyst:
quote:
ATI’s all-new Catalyst Control Center goes far beyond traditional driver configuration software—it’s a feature-rich and stable 3D acceleration control application that puts you in complete command of your ATI visual processing unit (VPU). Catalyst Control Center offers exceptional graphics performance and visual quality for the ultimate in performance, stability, and innovation. Safe GPU overclocking, custom profiles, and assignable hotkeys are just a few of the many new features. You’ll also enjoy frequent updates, reliable customer service, and an interactive user feedback program, all backed by ATI’s technical confidence, industry-leading capability, and uncompromising commitment to creating your ultimate visual experience.
Other than configuration purposes, it is not needed to function properly.