System is overheating, help needed.

[themenucha]

Hi! I have a problem: my PC is overheating... My system is:
Athlon x2 4600
arctic cooling freezer 7 pro rev2
EZcool maximum power 400W real
Gigabyte GA-MA790X-UD4P mobo
2 gb ddr2 800MHZ cl4 OCZ platinum
gigabyte hd 3870 512mb
250 bg HDD WD sata
My system is not overclocked. CPU goes from 40C to 90C and the system just shuts down, without BSOD or somethin, power goes off.(under full load). I tried a weaker graphic cards(X600/X1050), another PSU( corsair 500W) and HDD.I've installed the HSF properly,whith good thermal paste etc.I also have a few extra fans inside my ATX case...Now I'm trying to run "hot cpu" test- system is barely responsive and works under full load(both cores) at 80C WITH EXTERNAL FAN ADDED(not cpu A REGULAR FAN).A've played with my BIOS configuration and lowered my CPU and RAM voltages and even underclocked my CPU... I guess that my CPU or mobo are defected.(or both) How can I check or fix this?Thank you, Cyril.

 

[o1die]

Touch the base of the heatsink with your finger; if it doesn't burn your finger, then the board is putting out wrong readings and is shutting down the system to prevent damage to the cpu. You may need to flash the bios or get another board.

 

[themenucha]

Thanks!
I can touch the base of my heatsink with my finger without burning. now it shows 76C with 90% load(but there's nothing working) Anyway, I'll reflash my BIOS. Thanx again