  The non-commutative algebra which defines the theory of zero-branes on
$T^4/Z_2$ allows a unified description of moduli spaces associated with
zero-branes, two-branes and four-branes on the orbifold space. Bundles on a
dual space $\hat T^4/Z_2$ play an important role in this description. We
discuss these moduli spaces in the context of dualities of K3
compactifications, and in terms of properties of instantons on $T^4$.
Zero-branes on the degenerate limits of the compact orbifold lead to fixed
points with six-dimensional scale but not conformal invariance. We identify
some of these in terms of the ADS dual of the $(0,2)$ theory at large $N$,
giving evidence for an interesting picture of "where the branes live" in ADS.
