To compare the proportion of patients whose plasma HIV-1 RNA level falls and remains below the limit of quantification by the Roche Amplicor Monitor (400 copies/ml)[AS PER AMENDMENT 8/4/98: 50 copies/ml] between weeks 0 and 24. To determine the short-term safety and tolerability of MKC-442 plus nelfinavir (Viracept) plus dual nucleoside analogs. To determine the time to viral failure and time to tolerability failure through Week 48 of therapy.