Racivir ® (RCV) is an experimental drug which means it is not approved for use by the United States Food and Drug Administration (FDA), but it can be used in research studies like this one. RCV (Racivir®) is part of a class of drugs known as "Nucleoside Reverse Transcriptase Inhibitors" (NRTIs), which are intended to block a further increase in the amount of HIV virus in the body. Laboratory research suggests that RCV (Racivir®) may be effective in patients who have developed resistance to other NRTIs, particularly 3TC (lamivudine, Epivir®). However, a study of RCV (Racivir®) has not been done with patients who have previously been treated with other HAART (Highly Active Antiretroviral Therapy -- taking multiple HIV drugs at once) medications including 3TC (lamivudine, Epivir®).