Equivalence of Boosted Atazanavir Based Regimens and Currently Effective HAART Regimens

The primary objective of this study is to determine if Atazanavir and Ritonavir together will be as effective as the child's previous regimen in keeping the level of virus in the blood stream at such a low level it can't be found and whether that combination will be as effective as the previous regimen in keeping the infection fighting cells in the blood at the same level. Secondary objectives will be: * To determine if cholesterol and triglyceride levels drop in children switching to Atazanavir and Ritonavir from other medication regimens. * To evaluate if Atazanavir and Ritonavir result in an increase in patient satisfaction and patient reported adherence and a decrease in symptoms related to medication side effects. Inclusion Criteria are: * On the same medication regimen at least 3 months * Weight equal to or greater than 25kg * Able to swallow pills or willing to learn * Have a parent or guardian willing and able to sign informed consent * Not be taking a medication which interacts with Atazanavir * Not be currently taking Sustiva