  The aim of this paper is to clarify the relation between the following
objects: $ (a) $ rank 1 projective modules (ideals) over the first Weyl algebra
$ A_1(\C)$; $ (b) $ simple modules over deformed preprojective algebras $
\Pi_{\lambda}(Q) $ introduced by Crawley-Boevey and Holland; and $ (c) $ simple
modules over the rational Cherednik algebras $ H_{0,c}(S_n) $ associated to
symmetric groups. The isomorphism classes of each type of these objects can be
parametrized geometrically by the same space (namely, the Calogero-Moser
algebraic varieties); however, no natural functors between the corresponding
module categories seem to be known. We construct such functors by translating
our earlier results on $\A$-modules over $ A_1 $ to a more familiar setting of
representation theory. In the last section we extend our construction to the
case of Kleinian singularities $ \C^2/\Gamma $, where $ \Gamma $ is a finite
cyclic subgroup of $ \SL(2, \C) $.
