Wind turbine having a rotor, a nacelle frame (13) housing with electrical generation means coupled to the rotor hub (11), braking means and control means of the drive train rotational position, the nacelle frame (13) and the rotor hub (11) having an arrangement for preventing the rotor hub (11) rotation when certain maintenance or assembly activities should be carried out, the arrangement including at least one sliding pin (21) in the nacelle (13), first actuating means (31) for pushing/pulling it axially into/from at least one corresponding hole (23) in the rotor hub (11) and means for allowing vertical and lateral adjustment displacements of the sliding pin (21) so that it can remain concentrically aligned with the hole (23) when it is inserted into it.