I have the asus a7n8x-e mobo and a Radeon 9800 pro 256Mb with 1Gb of PC 3200 DDr corsair memory, Running Athalon 3200 xp pro and Win xp srvce pack 2.
Getting rainbow spots on screen when gaming only.

Two of my friends had that happen on their 9800 Pro's as well. One of them was using some CPU temperature monitoring and card overclocking tool and underclocked the video card to get rid of them. Another friend had a fan that wasn't working very well (if at all) on the card, and when he bought a new video card fan at the store and we put it on the random dots went away. Essentially I believe it is a heat issue.