actually it's a laptop, it's Dell Inspiron 7352. An Intel community expert told a random guy that maybe the motherboard have been overheated to death because of the bad heatsink or "not-enough" cooling system. and maybe that's right, my laptop has a cute tiny heatsink with 3.0GHz core i7.
My friend also had that problem with his DESKTOP while trying to play some heavy games on his integrated GPU, he DID also replace the motherboard :)