I have a pretty similar system (Win 7, 8gigs of Ram, Phenom II QC, ATI 5770). It runs everything pretty smoothly and nothing is overclocked. I have the fan set for 50% and it stays around 60-65c even after a few hours of play. Just make sure your case has good airflow and adding a few more fans never hurts and you can get decent case fans fairly cheaply off Newegg.com or Tigerdirect.
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