That Athlon 64 X2 4200+ has a max temp range of 55C to 70C. So avoid playing games first, at least for now. Take off the heatsink and clean it; no need to take off the processor for this, as people sometimes have problems putting it back. Clean off the old Thermal Paste with Isopropyl Alcohol. Reapply new Thermal Paste and then put back the AMD Stock HSF back on, presumably already clean and dry. Then recheck your temperatures.
I must say though, it appears you really will have to purchase a much better Aftermarket HSF. Perhaps a CoolerMaster Hyper TX3 or it's equal in performance, or even better than this.
Bytheway, is there an AutoShutDown Temperature feature on the BIOS? If so, at what temperature is it set? You should set it at 55C to be safe. Also, there have been issues regarding Athlon 64 X2 Processors wherein they give false temperature readings that are way too high. This is also a possibility as i had an X2 5000+ two years ago that would read 90C at 100% CPU Load, which actually was a false reading. To test against this possibility, before cleaning the AMD Stock HSF, first check if at such high temps the HSF is very hot to the touch. For instance, at 100C it should already burn you as that is already the boiling point of water. So just try this physical "test" at a lower temp then- at 50C for example, the HSF should be very hot but still touchable. If it's actually just warm at this temp, then the Athlon X2 4400+ is also giving a false temp reading like mine did.
