Hah, my machine is a P3-450, GeForce2, 384mb Ram, and the Special effects demo looks fine - same as the other examples (about 50 FPS).
You're using both the 'evil' technologies (AMD, and ATI, as opposed to Intel and nVidia) - maybe that's why
(Just kidding
![Smile :)](./images/smilies/icon_smile.gif)
)