Ati Tray Tools is no longer facing the issues described in the below article, but it does have an atipdlxx.dll error now. To fix the error you just need to put the dll file into your /Ati Tray Tools directory. Download the atipdlxx.dll here. (mirror)
Alternately you can download the installer (attsetup.exe) and the dll (atipdlxx.dll) in one go:
Everything below this line was relevant during Windows 7 release candidate – you don’t need to follow these step, it is just a reference.
As stated earlier, Windows 7 requires digitally signed drivers. This is a bummer if you want to run an awesome application like ATT rather than the inferior and bulky CCC. The fix, as you may have guessed, relies on DSEO. Download it, run it, agree to prompts, enable TEST MODE, and reboot.
Following the reboot, install ATT but do not launch it. Instead, head over to its installation directory and locate atitray64.sys and atitray.sys – these are the unsigned drivers.