:-O
well yeah personally I think it's impossible, becuase you need the software which is the "mind" and the CPU is what it runs on like a "brain"!
well that's how I think of it!
so far, we really have no clue as to how to create a sentient program, either becuase we lack the programming ability (maybe the code would be WAY to complex?), or because we don't have enough computing power to get anywhere near sentience.. (spelling's not right on that...)
BUT this made me think of something new.. a Distributed consciousness! cool idea? basically every participant computer runs the same software, which works while the computer is on the net, to contribute to running the software that is required for consciousness (which as above, I theorize that the complexety would require insane amounts of computer power).