If you really can’t find a replacement fan (which most people can’t) just gently clean the top of the CPU and back of the cooler fan with a cotton swab and and an alcohol wipe and gently re-apply some new thermal paste to both the top of the CPU and back of the cooler. What happens is the thermal paste dries out after a few years due to the CPU’s excessive heat thus causing the CPU to gointo thermal shutdown. My R600 works fine now and the entire job only takes 30 ~45 minutes and anyone who can use a use a small phillips screwdriver should be able to do this job without much difficulty. Just be sure to have 3 or 4 small containers to hold the different size screws and be careful as the screws are very very small and can get lost extremely easily if one is not careful. Also, clip the buds off a cotton swab and use this little stick to help you remove the CPU attachment end of the fan where it attaches to the motherboard.