Actor Michael J. Fox is known to millions for the "Back to the Future" films and the TV series "Family Ties" and "Spin City." But for the past two decades it's been his battle with Parkinson's disease, and his search for a cure, that may have generated the most attention. Looking back, he tells anchor Jane Pauley that sharing his battle publicly and joining with others to raise money has been "one of the great gifts of my life." He is now launching an online study to help researchers develop new therapies for the disease.