I have a noisy Acer laptop... I believe it is the main fan that causes most of the trouble. I have tried tweaking both the speed on the CPU and the GPU, but nothing helped.
What finally did the trick was removing the battery from the PC. After I did that, the fan runs slower and most of the noise is gone.
My theory is that even when the PC is connected to the wall socket, the battery produces heat which makes the fan run faster.