Houston--Dell Computer Corp. and Electronic Data Systems Corp. have entered a broad b-to-b marketing alliance. Dell, the world's largest PC maker, will market its computers to businesses combined with the consulting services of Plano, Texas-based EDS, the world's second-largest independent systems consulting company. (IBM Corp. is the largest.) EDS, meanwhile, will increase its use of Dell servers and other hardware during its consulting engagements. It is the latest move by Dell to expand its presence in the lucrative consulting field, amid a slowdown in PC sales.