This is a rollover protocol for patients previously enrolled in ACTG 320. Group A will involve a Phase II, randomized, double-blind, placebo-controlled study of 1592U89 in combination with zidovudine (ZDV), lamivudine (3TC), and indinavir (IDV) in NNRTI-naive and experienced subjects who have received (and are continuing to receive) ZDV (or d4T) + TC + IDV and have plasma HIV-1 RNA concentrations <500 copies/ml at screening. Group B will involve a Phase II, randomized, controlled evaluation of 1592U9 (vs. approved nucleoside analogs) and nelfinavir/NFV (vs. placebo) in combination with DMP-266 + adefovir dipivoxil in NNRTI-naive subjects who have received (and are continuing to receive) ZDV (or d4T) + 3TC + IDV and have plasma HIV-1 RNA concentrations > or = 500 copies/ml at Screening. Group C will involve a Phase II observational cohort of approximately 40 NNRTI-naive, ACTG 320 subjects with screening plasma HIV-1 RNA concentrations of 500-2000 copies/ml until approximately 16 weeks prior to the anticipated closure of Group B and followed until the closure of Group B.