Microprocessor cooling fan not working

Can anyone help me? My computer suddenly shutdown when I was surfing the net. Then, I switched it on but it doesn't work. I tried it three times but there's still no power..Then, I checked the connections if everything is in good grip. After that, my computer powered on.

However, after using it about two times it suddenly didn't work again. Whenever I switched it on, the power led will light up and the fans will work but that only lasted for 3-5 seconds and it will turn off. I tried it several times but it doesn't really turn on.

I don't know what to do. I tried using a different power supply, a different power switch and I also cleaned all the fans inside but still it doesn't work. I don't know what the problem really is but the microprocessor cooling fan is also not working. Is the problem concerns my motherboard? Is it dead? Do I have to replace it??

It's a triple core computer and i have a video card on board.