  Deformed preprojective algebras are generalizations of the usual
preprojective algebras introduced by Crawley-Boevey and Holland, which have
applications to Kleinian singularities, the Deligne-Simpson problem, integrable
systems and noncommutative geometry. In this paper we offer three contributions
to the study of such algebras: (1) the 2-Calabi-Yau property; (2) the
unification of the reflection functors of Crawley-Boevey and Holland with
reflection functors for the usual preprojective algebras; and (3) the
classification of tilting ideals in 2-Calabi-Yau algebras, and especially in
deformed preprojective algebras for extended Dynkin quivers.
