  The aim of this paper is to compare the two cases of an isolated neutron
star, with a non-accreted crust, and that of an accreting neutron star, with an
accreted crust, and try to estimate which one of the two would make a better
source of gravitational waves. In order to do this we must evaluate the maximum
``mountain'' that the crust can sustain in these two cases. We first do this
using the formalism of Ushomirsky, Cutler and Bildsten (2000) and find that the
maximum quadrupole is very similar in the two cases, with the non-accreted
crust sustaining a slightly larger mountain. We then develop a perturbation
formalism for the problem, that allows us to drop the Cowling approximation and
have more control over the boundaries. The use of this formalism confirms that
there is not much difference between the two cases, but leads to results
approximately one order of magnitude larger than those we obtain with the
formalism of Ushomirsky, Cutler and Bildsten (2000).
