Huge overheating problem

Is the 100c the case temp or the temp of a specific component? Do you smell something burning?

If it's the CPU that is overheating it might be as simple as cleaning up the heatsink and reapplying thermal compound. If it's the case temp I'd say somewhere in there you have a fan that's failing, turned the wrong way, or just not powerful enough. The PSU fan might have died - check that out and give it a good whiff. If you smell burning circuits in there, time to replace that puppy.

I have this tool called "Core temp" And it tells me the CUP temp. and no i dont smell anything burning. and i will try cleaning the heatsink and the fan for it blows in towards the heatsink

Could be your heatsink.

Remove and re-apply your thermal paste so the contactr between your CPU and heat sink are as thin as possible. Thicker thermal paste can act as an insulator... adding to the heat problem instead of drawing it away.
Use string or wire ties to move your ribbon cables so as to redirect airflow.
Heat Sink and fan combinations are very inexpensive... you might look for a better choice for your case. Adding another case fan can cost you no more than $7.00. You might also look at your power supply to see if it is moving air in and out as rapidly as needed.
Adding an exhaust fan to move hot air out can also help.
You really don't want those temperatures to get above 65c for very long...

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.