For participants whose initial regimen failed, or who experienced clinical disease progression (indicated by the development of a new CDC Category C diagnosis) or other clinical disease progression at or after Week 24 of first-line therapy, second-line therapy was strongly encouraged. (However, if poor adherence was suspected as a possible reason for an increase in HIV viral load, the site and the clinician were to try to improve patient adherence and obtain additional confirmatory viral load values within a five-week time frame.) In second-line therapy, participants who initially took NRTIs with a PI switched to NRTIs and an NNRTI. Participants who initially took NRTIs and an NNRTI switched to NRTIs and a PI. The timing of the switch was based on the participant's group: Groups PI/1K and NNRTI/1K switched to second-line treatment when viral load was 1,000 copies/ml or greater; Groups PI/30K and NNRTI/30K switched to second-line treatment when viral load was 30,000 copies/ml or greater. Participants who failed second-line therapy discontinued study treatment and were offered the best available therapy at the discretion of the clinician.