The purpose of this study is to compare the safety and effectiveness of 2 anti-HIV drug combinations in HIV-infected patients. Both combinations will include nevirapine (NVP), 2 nucleoside reverse transcriptase inhibitors (NRTIs), and at least 1 protease inhibitor (PI). One combination will include a new protease inhibitor, ABT-378, combined in a capsule with ritonavir (RTV).

Patients receive 1 of the following:

1. ABT-378/RTV plus NVP plus 2 NRTIs; or
2. Investigator-selected PI(s) plus NVP plus 2 NRTIs.

Inclusion Criteria

Patients may be eligible for this study if they:

• Are at least 12 years old.
• Are HIV-positive and have a viral load (level of HIV in the blood) of 1,000 - 100,000 copies/ml.
• Are currently taking an anti-HIV drug combination that includes 1 PI and 2 NRTIs, and that has not been changed in at least 12 weeks.
• Are naive to (have never taken) at least 1 NRTI, other than zalcitabine or abacavir.
• Agree to abstinence or use of an effective barrier method (e.g., condom) of birth control.

Exclusion Criteria

Patients will not be eligible for this study if they:

• Have an active illness.
• Have received treatment for any active opportunistic (AIDS-related) infection within 30 days of study entry.
• Have ever received a nonnucleoside reverse transcriptase inhibitor (NNRTI).
• Have received investigational (not yet approved by the FDA) drugs within 30 days of study entry.
• Have received treatment with a PI other than their current PI.
• Are receiving chemotherapy for cancer.
• Are pregnant or breast-feeding.