The purpose of this research study is to compare changes in triglyceride and other lipids (levels of fats found in the blood) from Baseline (Day 1) to Week 12 for darunavir/ritonavir 800/100 mg once daily versus atazanavir/ritonavir 300/100 mg once daily in combination with a fixed-dose background regimen consisting of emtricitabine [FTC]/tenofovir [TDF] 200/300 mg once daily). This study will also evaluate the safety (adverse events), effectiveness, and tolerability of darunavir/ritonavir and atazanivir/ritonavir over 48 weeks.