So the fan is not turning at all, or it turned momentarily.
Two possibilities:
* Faulty power supply.
* The motherboard has a short-circuit in it, preventing the power supply from working.
What Now?
1. Turn off the power supply.
2. Remove plug P8 from the motherboard, as shown in the following photo.
3. Turn on the power supply.
Click here if the power supply fan is now turning (continuously).
Click here if the power supply fan turned for a fraction of a second and then stopped (i.e. turned momentarily).
Click here if the power supply fan never turned.