1. Get those fans running. You NEED air running through your PC, that CPU fan Isn't good enough.
2. Have you checked/Do you know the voltage of the CPU? That might have an effect.
3. Clean out all of the dust in there. Dust doesn't conduct heat well. Use some compressed air or something.
4. You might want to consider removing the CPU fan and cooling pins and apply some thermal paste. Remember not to apply TOO much, about the size of a pea will do.
5. If all else fails, there's some basic water cooling kits, like the Corsair Hydro series of coolers. A bit overkill, I know, but it's better than getting your CPU toasted.
Also, keep the air in your area nice and cool, computers like that.