Safety and Effectiveness of Giving Adefovir Dipivoxil Plus Abacavir Plus Efavirenz Plus Amprenavir to HIV-Infected Patients Who Have Failed to Respond to Previous Protease Inhibitor Treatment

Inclusion Criteria You may be eligible for this study if you: * Are HIV-positive. * Had an HIV level of at least 2,000 copies/ml after 6 months of treatment with at least 1 PI other than amprenavir (meaning you failed PI treatment). * Are at least 13 years old (need consent of parent or guardian if under 18). * Are able to complete the study. * Agree to use effective barrier methods of birth control, such as condoms, during the study. Exclusion Criteria You will not be eligible for this study if you: * Have certain serious medical conditions, including AIDS-related cancers (except Kaposi's sarcoma) that require treatment during the study. * Have ever taken or are allergic to adefovir dipivoxil, ABC, APV, EFV. * Are participating in another anti-HIV drug trial during this study. * Have taken certain medications within 30 days prior to study entry, including medications that affect your immune system. * Have been diagnosed with hepatitis within the past 30 days. * Abuse alcohol or drugs. * Are pregnant or breast-feeding. * Have ever taken NNRTIs. * Have ever taken ddI or d4T. * Have received chemotherapy or radiation therapy within 30 days prior to study entry.