The theoretical prediction of the enhancement of the maximum growth rate of the electromagnetic ion cyclotron instability, occurring in thermally anisotropic plasmas, in the presence of a cold plasma component was investigated by a computer simulation experiment. The plasma parameters used are Bp ≡8&pgr;np,wkT∥,p/B02=1 and kT∥,p=25 keV. Three relevant cases were considered: case I, pure warm (np,c=0) isotropic (ApmdT⊥,pp/TN,p-1=0) plasma; case II, pure warm (np,c=0) anisotropic (Ap=0.5) plasma; and case III, a mixed warm-cold (np,c/np,w=2) anisotropic (Ap=0.5) plasma system. The results of the investigation confirm the linear theory of the enhancement of the instability. Moreover, they show the evolution of the unstable plasma systems through their quasi-linear and nonlinear stages. These results are relevant for active magnetospheric experiments to be performed in the near future.