SpeedswitchXP is a CPU frequency scaling utility for Windows XP which allows the user to select power profiles. I leave mine to dynamic when on both external power and when on battery. So far, it’s doing a great job keeping the laptop cool and quiet by reducing CPU speed when the processing power is not required (which is about 95% of the time). Now the fan never turn on high.
I8kfan is a fan control application that allows the user to set fan speed profiles. Make sure you don’t force your fan speed too low or the heat can damage components. I don’t use this currently as I let Windows manage my fan speed, but it’s a useful utility to have.