Does anyone know a seller where I can purchase the heatsinks alone? It appears that they are usually bundled with the Radeon 2600 HD Pro card. Update: Hey guys. So I think I might be extremely lucky. I opened up my iMac and gave it a good cleaning. There was a ton of dust in the fans. After I put it back together, its been running very stable and not overheating. If anyone is going through the same problems, they might want to clean out the dust and try that first before buying any replacement parts. Thanks again for your help guys.