[AS PER AMENDMENT 7/5/00: Patients now receive treatment on Regimen 1, 2, 3, 4, 5, or 6. Regimen 1 consists of IDV, ritonavir (RTV), ddI, and HU. Regimen 2 consists of APV, RTV, ddI, and HU. Regimen 3 consists of IDV, RTV, abacavir (ABC), and 3TC/ZDV. Regimen 4 consists of APV, RTV, ABC, and 3TC/ZDV. Regimen 5 consists of IDV, RTV, ABC, d4T, and 3TC. Regimen 6 consists of APV, RTV, ABC, d4T, and 3TC.] Arm E: Patients receive IDV, APV, and 3TC/ZDV. [AS PER AMENDMENT 7/5/00: Patients now receive treatment on Regimen 7 or 8. Regimen 7 consists of IDV, RTV, and 3TC/ZDV. Regimen 8 consists of APV, RTV, and 3TC/ZDV.] Arm F: Patients receive IDV, APV, ddI, and d4T. [AS PER AMENDMENT 7/5/00: Patients now receive treatment on Regimen 9 or 10. Regimen 9 consists of IDV, RTV, ddI, and d4T. Regimen 10 consists of APV, RTV, ddI, and d4T.] [AS PER AMENDMENT 7/5/00: Patients already enrolled in Step 3 before site registration to Version 4.0 of this protocol have the option of receiving 1 of the appropriate new Step 3 regimens as outlined above or staying on their originally assigned Step 3 therapy.] [AS PER AMENDMENT 3/21/01: If virologic failure on Step 1 or 2 is confirmed, then HIV-1 RNA genotype resistance testing (in real-time, if possible) is performed. Patients receive 1 of the Step 3 drug regimens based on the results of the resistance testing.] Patients may co-enroll in metabolic, pharmacologic, immunologic, or adherence substudies.