Philosophy has tangled with this subject for thousands of years neuroscience has recently entered the picture. However I feel that neuroscience while having valid input into the subject neglects the spiritual. Then, we run into the problem of measuring a spiritual phenomenon such as free will. Neuroscience would say that it is strictly biological. Instinct, something a large enough computer would be able to compute the actions of every individual past and future. I see this as coming down to having a belief in a God or gods or a source which has consciousness that either created humanity through spiritual means or created humanity through breeding. Neuroscience would be the avenue of approach if humanity was created through genetic breeding leaving the human without any objective spiritual lives other than imagined religious experiences.
I propose a thought experiment in which we are all living in a static world. There is no past, there is no future; we are just here. Present is you, the present is just a name we use for our living experience. However, within the present is the infinite past and future. Before the big bang and after the universe is wrapped up and fades away; you will be here. How does this tie into free will? Free will exists on the macro level or spiritual level but is limited in the micro level in our human experience. Limited but not completely taken. However, a large enough computer would be able to predict with great accuracy your future and tell you your past based on your present.
Imagine Infinite Source
Now imagine the infinite source. This source set everything in motion and may or may not be interacting with humanity on a spiritual level. I would suggest that this source does interact with us on a spiritual level through the subconscious. This then limits free will even more than natural animal instinctual behavior as now the subconscious is being influenced by a creator source. One may ask does the creator source have free will. I think that we can ask the same of our spiritual selves as we are a part of the creator source. All is one. In conclusion free will and lack thereof are non-existent. The question is moot as it is our human existence which asked the question in the first place. The lower cannot know more than the higher. If the creator source possesses free will than so do we. If not we are ok as there is nothing we can do about it.
Moral of this little thought experiment is that you have nothing to worry about in life as all life is probably planned out for you in advance.
Just enjoy the ride!