We investigate the classical geometry generated by a stable non-BPS
D-particle. We consider the boundary state of a stable non-BPS D-particle in
the covariant formalism in the type IIB theory orbifolded by (-1)^{F_L} I_4. We
calculate the scattering amplitude between two D-particles in the non-compact
and compact orbifold and analyse the short and long distance behaviour. At
short distances we find no force at order v2 for any radius, and at the
critical radius we find a BPS-like behaviour up to v4 corrections for long
and short distances. Projecting the boundary state on the massless states of
the orbifold closed string spectrum we obtain the large distance behaviour of
the classical solution describing this non-BPS D-particle in the non-compact
and compact cases. By using the non-BPS D-particle as a probe of the background
geometry of another non-BPS D-particle, we recover the no-force condition at
the critical radius and the v2 behaviour of the probe. Moreover, assuming
that the no-force persists for the complete geometry we derive part of the
classical solution for the non-BPS D-particle.Comment: 36 pages, LaTeX, no figures; amplitude for moving particles and
analysis of short and long distance interactions included, some assumptions
clarified, references adde