  We revisit the problem of constructing instantons on ADE orbifolds R^4/\Gamma
and point out some subtle relations with the complex structure on the orbifold.
We consider generalized instanton equations on R^4/\Gamma which are BPS
equations for the Yang-Mills equations with an external current. The relation
between level sets of the moment maps in the hyper-Kaehler quotient
construction of the instanton moduli space and sources in the Yang-Mills
equations is discussed. We describe two types of spherically-symmetric
\Gamma-equivariant connections on complex V-bundles over R^4/\Gamma which are
tailored to the way in which the orbifold group acts on the fibres. Some
explicit abelian and nonabelian SU(2)-invariant solutions to the nstanton
equations on the orbifold are worked out.
