My CPU voltage was set to Auto. Honestly only since that one time did my PC restart itself it never did it again and plus lots of other guides online say they've overclocked this CPU at 4.2GHZ+ using the stock CPU and cooler.Try setting your CPU voltage core to 1.3V. I'd also reseat the heatsink with a better paste. AC5 isn't top dog these days anymore. Make sure you use 100% rubbing alcohol to clean the paste from the CPU and the heatsink. MX-4 works great. Be sure to use the pea method when applying paste too.