  A two-dimensional gas of non-interacting quasiparticles in a nearly periodic
potential is considered at zero temperature. The potential is a superposition
of a periodic potential, induced by the charge density wave of a Wigner
crystal, and a weak random potential due to disorder. There is a
metal-insulator transition that is controlled by the strength of the periodic
potential. The transition is continuous in the presence of randomness. We
evaluate the density of states, which is non-zero at the Fermi energy in the
metallic phase, and the dc conductivity. The latter changes with decreasing
modulation of the periodic potential from 0 to $\sigma\approx2e^2/h$.
