Ad agency J. Walter Thompson USA, New York, and Dell Computer Corp., Austin, TX, have settled a dispute stemming from the work the ad agency did in 1998 for the computer direct marketer, according to a Dell spokeswoman. The terms of the settlement were not disclosed. The agency had filed a suit against Dell in New York State Supreme Court last year seeking $6.33 million in damages after the computer company ended its three-month relationship with the agency, moving the brand-advertising business to BBDO Worldwide, New York. Dell then filed a countersuit, seeking unspecified claims. J. Walter Thompson had worked on Dell's "Be Direct" campaign.