Well let me try and put this as simply as possible...
If the actual pyhsical part of the card was broken, you would be having way more severe problems, you would not be able to use it. So, with that said, it is software related.
Whether the software is Windows, your drivers, the games, directX, spyware, or who knows, you need to start with reinstalling your video drivers.
Go to the ATI website and download the right ones for your card. After that, go to directX. If none of that works, then we can look further.
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