Anyhow, after eating our brunch, he opened up the CPU and cleaned it up. Gee, you won't believe how much dust was in there. 
It's been a while since we last clean it so the dusty parts inside made the fan stop functioning right. I was happy after he tidied it up because the computer is running smoothly now without a sound from inside. I am back to normal blogging now hehehe. I thought for sure it was the end of it because our PC is more than 3 years old already. Thanks God, it got fixed.. He knows we can't afford to get a new one lol..