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).