Thermalright Ultra 120 Extreme with a Silverstone FM121 120mm fan.
Thermalright Ultra-120 eXtreme CPU Heatsink - (Socket 775 / AM2) - FrozenCPU.com Newegg.com - SILVERSTONE FM121 120mm Case Fan - Case Fans
And your thermal paste can make an effect also. There are alot of options nowadays on thermal paste. I just did a thermal paste review at another site using 7 different pastes if you care to read it.
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