The PSU fan that starts but stops quickly usually means something in the system is loading the supply down.
Do as Sarrkazztic suggested. Unplug everything in the case, power cords, cables, etc. including power to the mobo.
Now plug power into one component only. Just use one of the 4 wire molex connectors to a hard drive, flop drive, cpu fan, etc, but only one device.
Turn on power and see if fan spins correctly. If yes, then you have to localize the problem. Unplug whatever you plugged in.
Now remove all boards except video card and memory, mobo (plug power cables back in mobo), hook up monitor and keyboard.
Now see if it will show a post on the monitor (power on self test) and make sure PSU fan is still spinning. If the monitor shows booting in progress, you'll have to start plugging all things back in, checking as you go, to see what is holding the PSU down. You'll probably have a loose connection somewhere.
If PSU fails to spin with one component hooked to power, the PSU is faulty.
Done this a million times. Easiest to localize and isolate this type problem.
Ground yourself occasionally by touching the metal PSU. Show your son how to do the grounding also, if he's not still grounded to his room.
BTW, I only know a 3 phase a/c motor can have the direction changed by changing 2 legs of the phase wiring. Well, I do know more than that but doesn't pertain to computer.