The cool thing here is that determinism is so convincing, and I don't think that it's something to be ashamed of. It's something to be exploited. If all of our actions can be calculated to be products of conditions in the world we live in, then it follows that you could simulate anyone's whole life just by giving a program the correct set of parameters to project your life's course. If that's true, then it also follows that with a sufficiently powerful and complex computer, the whole universe could be predicted from beginning to end just by giving it the right numbers. If that's true, then what's to say that it hasn't happened already and that we aren't all just living out a computer simulation designed to predict the future?
Moreover, what if we're just on the tip of the iceberg? What if we're a simulation within a simulation, etc., etc.? It stands to reason that any intelligent life that has developed a computer for predicting the course of the universe will eventually predict up to the point at which the universal simulator is developed, and the events proceeding that one will be dependent upon the outcome of the simulation, thus trapping the computer on an infinite simulation within a simulation generating loop. Given the probability that such a computer could be created and the likelihood that any civilization capable of creating such a thing would A) exist and B) carry it out, I think it's more probable that this situation is the case than it would seem.
So the real question then is, when will the system crash? How much time have we got before the great BSOD in the sky gets us all?
I think I'm supposed to be writing about free will vs. determinism, but I hate it and I won't.