I cannot believe in free will simply because for me, such a concept would require that a particular decision I take would have to be completely unencumbered by ANY pre-existing biases, influences, memories, etc. "Freedom" or "Free" the way I envision it, is the absence of all constraint. I can not think of any decision I have ever made in my life not influenced by prior experience, memories, or biases. I believe we inherit a genetic range within which our minds and bodies may operate, but we are still operating within the confines of these limits in everything we do, and every decision we make. This does not however make us unaccountable for our actions because we still have "circumscribed" choices that we can make within the confines of the moral universe we (or our specific society) constructs for us.
Even the decisions we make with biological implications are governed by homeostatic, physiological processes (sex, the food we eat, the liquids we seek, etc).