i do it in two different ways. my bios allows me to set the speed of the fan 25-40, 60,100 percent.
second way i do it is with the aod program from amd. (overdrive). there you have options for overclocking and fan speed control.http://game.amd.com/us-en/drivers_overdrive.aspx
sorry about the link to newegg, but here are is a good website for reviews and comparisons of heatsinkshttp://www.frostytech.com/top5heatsinks.cfm
hope it helps you out.