  Magnetoconvection in a tall vertical box with vertical hot and cold walls,
and an imposed steady uniform magnetic field perpendicular to the temperature
gradient, is analyzed numerically. The geometry and the values of the
non-dimensional parameters - the Prandtl number of 0.025, the Rayleigh number
of $7.5 \times 10^5$, and the Hartmann number between 0 and 798 - match those
of an earlier experiment. A parametric study of the effect of wall electric
conductivity, across a wide range of conductance ratio values, on flow
properties is performed. Two configurations of electric boundary conditions are
explored. In one configuration, all walls have finite electric conductivity,
while in the other, only the walls with constant temperature are electrically
conducting. The flows are analyzed using their integral properties and
distributions of velocity, temperature, and electric currents. It is found
that, in general, the convection flow is suppressed by the magnetic field.
However, this effect is strongly modified by the wall's electric conductivity
and is markedly different for the two wall configurations. The associated
changes in flow structure, rate of heat transfer, and flow's kinetic energy are
revealed. It is also shown that the assumption of quasi-two-dimensionality may
not be valid under some conditions, even at high Hartmann numbers.
