Well, they ARE his pictures, so he has every right to have a copy of them. The touchy situation is going on Friend A's computer without his approval, but it can be justified in that he really isn't supposed to have those pictures in the first place, and you didn't delete or go through any of his stuff.
Of course, the dishonest thing would be to delete them, see how long it takes him to nitice, and then deny the whole thing.
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