Christopher Chan wrote: >> It is a 4-pin connector, and I think there is a guide, or one side is >> different than the other. That is why I think I could not have but in in >> backwards. >> > > Okay, not the stuff you get on boards that are not 'branded'. > MANY newer desktop CPU fans are 4 pin... this way there is power, tach output and PWM control on separate pins (and ground).... doing PWM speed modulation on a 3 pin fan makes reading the tach kind of hard. but, as you noticed, we are dealing with a HP NC2400 laptop here. http://h10010.www1.hp.com/wwpc/us/en/sm/WF06a/321957-321957-64295-321838-306995-1847110.html