  We present a detailed numerical analysis of the effect of a magnetic field on
the transport properties of a `small-$N$' one-sided surface disordered wire.
When time reversal symmetry is broken due to a magnetic field $B$, we find a
strong increase with $B$ not only of the localization length $\xi$ but also of
the mean free path $\ell$ caused by boundary states. Despite this, the
universal relationship between $\ell$ and $\xi$ does hold. We also analyze the
conductance distribution at the metal-insulator crossover, finding a very good
agreement with Random Matrix Theory with two fluctuating channels within the
Circular Orthogonal(Unitary) Ensemble in absence(presence) of $B$
