  The study of brane-antibrane configurations in string theory leads to the
understanding of supersymmetric D$p$-branes as the bound states of higher
dimensional branes. Configurations of pairs brane-antibrane do admit in a
natural way their description in terms of K-theory. We analyze configurations
of brane-antibrane at fixed point orbifold singularities in terms of
equivariant K-theory as recently suggested by Witten. Type I and IIB fivebranes
and small instantons on ALE singularities are described in K-theoretic terms
and their relation to Kronheimer-Nakajima construction of instantons is also
provided. Finally the D-brane charge formula is reexamined in this context.
