Michael J. Fox stars in TV spots for Gateway as someone who wants a deal-the best computer for less than $1,000. In "$999, No AOL," the actor says: "I want a really cool computer... . I want speed... . I want a humongous monitor... . Everything." Gateway got the spots on air just seven days after the Jan. 12 shoot. Agency: McCann-Erickson, New York. Executive VP, deputy creative director: Irwin Warren. Senior VP-group account director: Peter McGuinness. See related item on P. 32.