Patients are grouped according to age. Group A consists of patients between the ages of 13 and 30 years. Group B consists of patients age 45 years or older. All patients receive open-label lopinavir/ritonavir (LPV/RTV) plus emtricitabine (FTC) plus stavudine (d4T) for 96 [AS PER AMENDMENT 06/04/02: 192] weeks. Study visits occur at pre-entry, entry, and Weeks 4, 8, 12, 16, and 24 then every 12 weeks thereafter through Week 96 [AS PER AMENDMENT 06/04/02: Week 192]. Clinical assessments, safety laboratory tests, CD4 cell count monitoring, lymphocyte phenotyping, and HIV-1 RNA determinations are performed routinely. Blood samples are stored for further immunology and virology studies. Patients may volunteer to participate in virology substudy A5020s and either immunology substudy A5016s or A5017s [AS PER AMENDMENT 06/04/02: Substudy A5017s has been eliminated.]