Changing Fan Speed? (SATA -> MOLEX)

Hi, I've just bought a 120mm fan and i am actually connected to all 3 of these 120mm blue led fans into 1 sata power to molex connector my concern is the speed of the fan. It's running really fast which keeps my system nice and cool but it's really loud and I'm not sure if it is possible to change the fan speed using MOLEX. The molex is for the fan spinning and the led but it also has a 3 pin with one yellow wire connected directly into the 3 pin plugin on my motherboard so i assume there is a way to control the voltage? I don't want it to burn out or anything like that they are expensive fans. I know there is a program called speedfan but it is really hard for me to understand it. Is there an alternative FREE program? and is it possible to change the speed to all 3 fans?