HIV-infected patients taking NRTI drugs may have an increase in a chemical in their blood called lactate. High lactate levels may damage the energy source of the cell (mitochondria). Damage to mitochondria may cause lactic acidosis, liver failure, and other problems. It is important to find effective ways to see if the mitochondria of HIV-infected patients have been damaged. This study will see if MRS can be used to determine mitochondrial damage.