Need PC help? 10 points?

Is there a way of raising the temperature setting on a Dell dimension 3000. The fan racing problem is not dirt or the fan, I seen so many posts online saying that the problem is in the settings. Dell has the setting very low, that's why the cpu fan (with the green shroud) races so loud in the summer and runs so quiet in the winter. It's literally like two different machines (based on the room temp). It has a P4 2.8 chip. Any way of tweaking and correcting the settings..