This study compares 2 different anti-HIV drug regimens to determine which is the most effective in lowering the amount of HIV in the blood. The anti-HIV drugs used in this study are 2 protease inhibitors (nelfinavir and ritonavir), 2 nucleoside reverse transcriptase inhibitors (stavudine and didanosine), and 1 nonnucleoside reverse transcriptase inhibitor (nevirapine).