This protocol is a stratified, randomized, double-blind, dose-comparative study of the safety and efficacy of adefovir dipivoxil in combination with nelfinavir and saquinavir soft gel capsules (SGC) or adefovir dipivoxil in combination with nelfinavir or saquinavir SGC plus a nucleoside analog (zidovudine, lamivudine, or stavudine).