  The particle spectrum of the supersymmetric extension of the standard model
with a gauge singlet is studied. Soft supersymmetry breaking terms are
explicitly chosen to be non-universal according to orbifold string theory. they
depend on modular weights of chiral fields and on an angle $\theta$ specifying
the supersymmetry breaking sector. Imposing radiative weak symmetry breaking
and requiring that standard model Yukawa couplings should be allowed yield
constraints on modular weights and almost specifies the angle $\theta$. We then
perform a numerical anlysis of the low energy spectrum. It turns out that the
spectrum is very constrained, revealing salient features such as light Higgses
and neutralinos. The latter turns out to be essentially gaugino-like.
