  Based on the recently discovered K-theory description of D-branes in string
theory a K-theory interpretation of the topology of gauge conditions for four
dimensional gauge theories, in particular 't Hooft abelian projection, is
presented. The interpretation of the dyon effect in terms of K^{-1} is also
discussed. In the context of type IIA strings, D-p branes are also interpreted
as gauge fixing singularities.
