  We propose a new method to compute the configurational entropy of glassy
systems as a function of the free energy of valleys at a given temperature, in
the framework of the Stillinger and Weber approach. In this method, which we
call free-energy inherent structures (FEIS) approach, valleys are represented
by inherent structures that are statistically grouped according to their
free-energy rather than the energy as is commonly done in the standard
procedure. The FEIS method provides a further step toward a description of the
relaxational behavior of glassy systems in terms of a free energy measure. It
can be used to determine the character of the glass transition as well as the
mode coupling and the Kauzmann temperatures. We illustrate the usefulness of
the method by applying it to simple models of glasses and spin glasses.
