At what point should an intelligent machine be considered a person?

Science fiction likes to depict robots as autonomous machines, capable of making their own decisions and often expressing their own personalities. Yet we also tend to think of robots as property, and as lacking the kind of rights that we reserve for people. But if a machine can think, decide and act on its own volition, if it can be harmed or held responsible for its actions, should we stop treating it like property and start treating it more like a person with rights? What if a robot achieves true self-awareness? Should it have equal rights with us and the same protection under the law, or at least something similar?