  We analyze $N=2,1,0$ vacua of type IIB string theory on $K3\times T^2/Z_2$ in
presence of three-form fluxes from a four dimensional supergravity viewpoint.
The quaternionic geometry of the $K3$ moduli space together with the special
geometry of the NS and R-R dilatons and of the $T^2$-complex structure moduli
play a crucial role in the analysis. The introduction of fluxes corresponds to
a particular gauging of N=2, D=4 supergravity. Our results agree with a recent
work of Tripathy and Trivedi. The present formulation shows the power of
supergravity in the study of effective theories with broken supersymmetry.
