  The D1/D5 system is considered in the presence of the NS B field. An explicit
supergravity solution in the asymptotically flat and near horizon limits is
presented. Explicit mass formulae are presented in both cases. This solution
has no D3 source branes and represents a true bound state of the D1/D5 system.
We study the motion of a separated D1-brane in the background geometry
described above and reproduce the Liouville potential that binds the D1 brane.
A gauge theory analysis is also presented in the presence of Fayet-Iliopoulos
(FI) parameters which can be identified with the self-dual part of the NS B
field. In the case of a single D5-brane and an arbitrary number of D1 branes we
can demonstrate the existence of a bound state in the Higgs branch. We also
point out the connection of the SCFT on the resolved Sym$_{Q_1Q_5}(\tilde T^4)$
with recent developments in non-commutative Yang-Mills theory.
