  To a finite quiver equipped with a positive integer on each of its vertices,
we associate a holomorphic symplectic manifold having some parameters. This
coincides with Nakajima's quiver variety with no stability parameter/framing if
the integers attached on the vertices are all equal to one. The construction of
reflection functors for quiver varieties are generalized to our case, in which
these relate to simple reflections in the Weyl group of some symmetrizable,
possibly non-symmetric Kac-Moody algebra. The moduli spaces of meromorphic
connections on the rank 2 trivial bundle over the Riemann sphere are described
as our manifolds. In our picture, the list of Dynkin diagrams for Painlev\'e
equations is slightly different from (but equivalent to) Okamoto's.
