HIV protease inhibitors (PIs) are a class of antiretroviral drugs used to inhibit viral replication. They do so by interfering with a key step in the replication process. Some HIV PIs have been associated with an increased risk of adverse cardiovascular side effects. Further study is needed, however, to assess the full extent of effect of newer HIV PIs, including atazanavir and lopinavir/ritonavir, on cardiovascular disease risk. This study will compare the effects of atazanavir, lopinavir/ritonavir, and placebo on certain cardiovascular disease risk factors in healthy people without HIV.