Every conceivable behavior is either deterministic, or random, or some combination of the two. Neither determinism nor randomness can possibly qualify as free will --- intuitively, neither a clock's gears nor a pair of dice possess free will --- and therefore the very concept of free will is philosophically incoherent.
To elaborate slightly, behavior either follows a set of predictable rules, or it does not. If behavior follows a set of predictable rules, then those rules constitute a deterministic algorithm, which clearly lacks free will. If behavior does not follow a set of predictable rules, then it is a random process, which clearly also lacks free will. In practice, most nontrivial behaviors must be modeled by a combination of deterministic and random elements, but combining the two into a randomized algorithm doesn't produce free will either.
Incidentally, all known physical processes --- or, in other words, all possible computing devices in the universe, including human neurons --- can be modeled using some combination of deterministic and stochastic processes. So, even if free will could conceivably exist, actual human beings certainly would not possess it. However, I believe that the very concept of free will is incoherent, an argument that does not depend on properties of our physical universe.
If you disagree with this analysis, it can only be because you misunderstand algorithms, or you misunderstand randomness, or you do not understand how these two combine, or you are defining free will in some tendentious fashion. This seems to be the case, for example, for most of the philosophical positions described in the Wikipedia entry on free will. Notably, none of the pro-free-will arguments that I've ever seen manage to distinguish human decision-making from, say, a program that repeatedly generates a random array, and then sorts that array using an implementation of quicksort that selects a random pivot on each recursion. If you believe that quicksort with a random pivot possesses free will, I suggest that you've redefined free will away to the point of uselessness.
Now, given that free will is philosophically incoherent, I'm not surprised that definitions of free will turn out to be useless, but still, it's sort of sad. Just give up already!