It's possible that the board is not getting power to the fan, as mentioned above. If you have a volt-meter this would be a good time for a continuity check. Check the power/ground pins coming off of the connector on the motherboard(do this with the laptop powered on; don't worry you won't hurt it).
To find your hot wire and ground wire look at the connector and find the corresponding pins on the motherboard connector. Most times they are color coded from the fan wires: red(hot); black(ground); yellow(signal). We are interested in red and black. Signal wire will tell fan to speed up or slow down. Probe what would be where the hot and ground wires connect to the board's connector and the meter will show you if there's anything coming through. The voltage coming off of the board that powers the internal laptop fans is usually a low voltage(3.3 or 5 volt).
Check this if you can, if you do and there's no voltage coming off of the board connector; could be a bad fan. I doubt that's the case. If the color coding for the wires is different than what I described, let me know and we can decipher what's what. If there's a blue wire, that could be your signal/control wire.
If there's not power coming out of the original cpu-fan connector, you can tap into your usb port's 5v connection. The first pin on usb is 5v and pin 4 is ground(see google for pinout), however you only have ~500ma of current to draw from the port. Your fan is probably rated at 200ma at least. This means that if you did this you probably wouldn't be able to use the usb port for anything else. Also, the fan will have no control wire so it would be running full blast all the time. At that point you could wire an inline potentiometer(looks like volume knob) to control the voltage going into fan(effectively speeding it up/slowing it down).