Let's just go through the basics:
- Make sure the power connector is secure and clean.
- Uninstall and reinstall the drivers for your card completely.
- Make sure nothing is accidently blocking the card's fan, like a loose wire or something.
- Try defaulting your bios, or just clearing them by taking the battery out and putting it back in a few seconds later (make sure your computer is unplugged). A setting like AGP voltage/speed could be off.
- Make sure the power connector is secure and clean.
- Uninstall and reinstall the drivers for your card completely.
- Make sure nothing is accidently blocking the card's fan, like a loose wire or something.
- Try defaulting your bios, or just clearing them by taking the battery out and putting it back in a few seconds later (make sure your computer is unplugged). A setting like AGP voltage/speed could be off.