The study will evaluate four different oral 1st line antiretroviral regimens: three study arms will contain different doses of Fozivudine (FZD) plus Lamivudine (3TC) in a twice daily or once daily application plus once daily Efavirenz. The 4th study arm will contain standard Zidovudine (AZT)/Lamivudine (3TC) twice daily in a fixed dose combination plus once daily Efavirenz. The treatment duration will be 24 weeks.