CPU Fan Speed

I've been doing some maintenance on a friends computer, running a P4 2.4 on an Asus P4G8X, and I'm having trouble with the processor fan speed. I can't get it to increase above 2400. Shouldn't this be running around 6000? There isn't any sort of throttle in the BIOS I can find, but I was wondering if having it connected to the wrong 3 pin connector on the motherboard would be problem, by supplying inadequate power. Kinda like plugging case fans into the "FAN ONLY" molex connectors. They never get up to speed so never move any air. Lots of his games randomly freeze up for 10-15 seconds when heat gets too high, and I was able to solve most of this by rewiring his case fans, but I'd like to increase the CPU fan speed for peace of mind. Any tips/ways I can do this?

Tech Support: "Hello, tech support, may I help you?"
Customer: (in a thick Russian accent) "Yes. Monitor is working fine but has sparks and smoke flying out back. Is ok?"