maybe the HS is not seated properly on the cpu. take it off, clean, and put it back on with arctic silver 5. someone else will be able to give more detailed instructions how to do this.
... ahem. Yes, you need to obtain a better cooling design here. It sounds like you bought this computer retail, as it sounds like a typical build with a funnel over your heatsink/cpu.
You essentially need to take off your heatsink and throw it in the garbage; buy a better aftermarket heatsink and fan with arctic silver 5 compound; get some more fans to move air through your system. You may also need to lower your room temps. And, for god sakes, clean the dust out of your case every once and awhile.