ACTG 377 is a Phase I/II, randomized, open label, multi-arm study with experimental therapies added in a rolling protocol format. The primary goal of ACTG 377 is to evaluate a series of combinations of antiretroviral agents with respect to the change in plasma HIV-1 RNA copy number, safety and tolerance, and to determine which of these therapies warrants investigation in a Phase III study. This study evaluates d4T/Nevirapine/ Ritonavir vs. d4T/3TC/Nelfinavir vs. d4T/Nevirapine/Nelfinavir vs. d4T/3TC/Nevirapine/Nelfinavir with respect to their ability to induce undetectable plasma HIV-1 RNA copy number and to reduce plasma HIV-1 RNA copy number by > 2 logs at 12 weeks.