In this open-label, multicenter study patients are randomized into 1 of 4 groups based on prior antiretroviral experience. Each regimen consists of 4 drugs that include a combination of nucleoside reverse transcriptase inhibitors (stavudine, lamivudine, zidovudine, didanosine, zalcitabine) plus nevirapine (NVP), nelfinavir (NFV), or ritonavir (RTV). Patients must be naive to at least 2 of the 4 drugs in the regimen and at least 1 of the novel drugs must be NVP, NFV, or RTV.