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We study the spectrum of stable BPS and non-BPS D-branes in Z_2 x Z_2orientifolds for all choices of discrete torsion between the orbifold andorientifold generators. We compute the torsion K-theory charges in these D=4,N=1 orientifold models directly from worldsheet conformal field theory, andcompare with the K-theory constraints obtained indirectly using D-brane probes.The K-theory torsion charges derived here provide non-trivial constraints onstring model building. We also discuss regions of stability for non-BPSD-branes in these examples.Comment: 40 pages, 5 table

D-brane spectrum and K-theory constraints ofD= 4, Script N = 1 orientifolds