[Note: As of 2/28/2001, due to toxicity studies and concerns for safety, sites were notified that they need to discontinue patients from the capravirine/placebo arms and continue patients with their background therapies or switch patients to new therapies, as deemed appropriate by the investigators.] Patients are randomized to receive one of two doses of AG1549 plus Viracept (nelfinavir) plus Combivir (zidovudine/lamivudine). Patients remain on their assigned therapy for 48 weeks, with a follow-up visit at 28 to 35 days after the last dose of study medication. Blood samples are taken regularly to quantify HIV-1 RNA, CD4 and CD8 counts, peripheral blood mononuclear cells (PBMC), AG1549, Viracept, and M8 plasma concentrations. Physical exams, safety assessments, and other tests are also done throughout the study. On Day 8 and at the end of Week 48, pharmacokinetic samples are collected at 0, 0.5, 1.0, 1.5, 2.0, 2.5, 3.0, 4.0, 6.0, 8.0, and 12.0 hours postdose. At the end of Weeks 4, 8, 16, 24, and 36, pharmacokinetic samples are taken prior to dosing and between 2 to 4 hours post-dose.