Looks like you're running the E8400 at factory clocks. If you're not using a locked motherboard (any of the mass market brand preconfigured PCs), the E8400 over clocks easily to 3.8-4.0 ghz. That might tax the factory heat sink, but the C2D chips run pretty cool. I had an E8400 clocked at 3.8 using a $20 aftermarket heat sink that ran so cool that I could have turned up the voltage for even higher clocks had I wanted.
I wouldnt do that without a good cooling system! Especially with a GPU like the nvidia Gtx 560ti inside.