  Pursuing further the recent methods in the algebraic Hamiltonian approach to
gauged WZW models, we apply them to the bosonic SL(2,R) X SU(2)/R^2 model
recently investigated by Nappi and Witten. We find the global space and compute
the conformally exact metric and dilaton fields to all orders in the $1/k$
expansion. The semiclassical limit $k',k\to \infty$ of our exact results agree
with the lowest order perturbation computation which was done in the Lagrangian
formalism. We also discuss the supersymmetric type-II and heterotic versions of
this model and verify the non-renormalization of $e^\Phi\sqrt{-G}$.
