Hmm, if you do not have the uninstall utility means there's a conflict going between the drivers. And did it went to standby itself? it means you need to uninstall the drivers properly, restart, make sure there's a pop-up find new hardware wizard. then install ati catalyst 6.12.
btw, when i did not update my computer graphics driver for 1 year, the computers shutted down whenever i throw a flash-bang but after updating no more problems. Another issue, my friends do not install any ATI software at all, but he still be able to play some 3D games. This indicate that proper drivers are needed in order to run 3D games properly.
So my last word is, try to do a proper installation of it, if you still cant get rid of it, you'll need to fix it physically or upgrade to a newer gpu (graphics processing unit)