AS PER AMENDMENT 10/20/97: For PRAM-1, Step 2: To evaluate d4T + nevirapine + ritonavir with respect to change in plasma HIV-1 RNA copy number from baseline to 48 weeks in children who have received at least 12 weeks of therapy on the PRAM-1 ZDV/3TC arm and have over 10,000 viral copies at weeks 12, 24, or 36. To evaluate the safety and tolerance of d4T + nevirapine + ritonavir based upon laboratory and clinical toxicities. [AS PER AMENDMENT 10/23/98: To evaluate safety and tolerance of a switch from d4T + ritonavir vs. ZDV + 3TC + ritonavir to d4T + indinavir vs. ZDV + 3TC + indinavir in stable, HIV-infected children with RNA values <= 10,000 copies/ml.] For PRAM-1: Evidence supports combination therapy with 2 or more antiviral agents as beneficial in the long-term management of HIV. The possibility exists that combination therapy may result in a synergistic or additive activity over a prolonged period of time. Also hypothesized is that the development of resistance to individual agents will be developed if viral replication is significantly decreased.