Is it possible to use coolers/fans as wind powered generators?
DC-powered fans often use a brushless permanent-magnet motor along with some control electronics.  The motor itself could act as a generator, but the electronics generally won't allow any power the motor could generate to escape.  Taking apart such a motor would likely allow one to make a generator, though I doubt it could produce much power.

Mains-powered fans often use a different style of brushless motor which won't work well as a generator unless there's already AC voltage present.  It's sometimes possible to use such motors as generators if one properly connects capacitors between the windings, and ensures that there is no load other than the capacitors until the unit has built up some voltage [residual magnetism in the motor's parts won't produce any significant power, but in the absence of a load it may produce enough to produce voltage to build up a magnetic field which would then be capable of producing significant power.  An interesting feature of motors used this way is that they have a limit to the amount of power they can supply without collapsing the magnetic field; trying to draw more than that will collapse the field and shut everything down.