This 2-part study will test the safety and anti-HIV activity of capravirine alone, and the safety, anti-HIV activity, and drug interactions of capravirine combined with other anti-HIV drugs. Capravirine belongs to a class of drugs called non-nucleoside reverse transcriptase inhibitors (NNRTIs), which are effective when used together with other drugs, including nucleoside reverse transcriptase inhibitors (NRTIs) and protease inhibitors.