My White Macbook (Mid 2009) was just too loud, no matter what I did, as if there was a small lawn mower is living inside the laptop. I suspected the CPU fan, so I followed this guide, and now everything is super-quiet! It turns out, I didn't have to replace the CPU fan. After disassembling everything, I took out the CPU fan. There were a lot of dust from years of neglect on the fan as well as the heat sink/air-flow area, and I cleaned as best as I could using Q-tips. There were clumps of black dusts. I also cleaned the inside of the fan, since it was very easy to disassemble. After removing all the dust and cleaning, I put everything back together.
Now, it's like night and day. I can't even hear the fan, even if I tried. What a change. It brought my Macbook from dead. . Thank you, iFixit, for such a thorough guide for repair.