Patients receive a treatment regimen consisting of didanosine, stavudine, delavirdine, and MKC-442 for 24 weeks. During the study, patients are evaluated for changes from baseline in plasma HIV-1 RNA levels and lymphocyte subsets and for development of adverse events and toxicities. Samples for population pharmacokinetics are collected from all patients every 4 weeks. Patients who experience virologic failure may add hydroxyurea to their treatment regimen or be discontinued from the study. Patients who add hydroxyurea to their regimen and subsequently experience virologic failure are discontinued from the study. After Week 24, patients with documented virologic response are eligible to continue receiving study treatment until their plasma HIV-1 RNA levels return to baseline levels. For patients receiving hydroxyurea beginning at Week 24, visits are conducted at Weeks 28, 32, 36, and every 12 weeks thereafter. For patients who continue taking didanosine, stavudine, delavirdine, and MKC-442 or who have started hydroxyurea treatment between Weeks 12 and 20, follow-up visits are conducted every 12 weeks, or sooner if needed, until the patient permanently discontinues study treatment.