Patients are randomized to 1 of 4 treatment arms. In Group 1, patients receive a dose of L-756423/IDV once daily plus IDV placebo. In Group 3, patients receive a lower dose of L-756423/IDV twice daily (with the daily dosage equaling that of Group 1) plus IDV placebo. In Groups 2 and 4, patients receive equal dosages of IDV plus L-756423/IDV placebo. In all 4 groups L-756423 and IDV are blinded to the investigator and patient. All groups receive open-label d4T and 3TC. Patients routinely undergo a physical exam and have blood and urine tests to ensure the drugs' safety and tolerability, which will be evaluated by tabulation of adverse events and clinical assessment of laboratory data. In addition, CD4+ T cell and plasma viral RNA levels are measured to quantify the drugs' antiretroviral activity.