 Patients enrolled in the study will be re-examined and have additional blood tests before beginning treatment with Fuzeon. They will then be taught how to self-inject the medicine under the skin and will take two doses daily less than 14 teaspoon each, 12 hours apart. After the first treatment, participants will have follow-up visits at weeks 1, 2, 4, 8, 12, 24, 36, 48, and every 12 weeks after that, if necessary, until 12 weeks after the drug becomes commercially available. Visits may be scheduled more often if a problem arises. During the follow-up visits, patients will have blood drawn, and their blood pressure, pulse rate and temperature will be checked. They will also report any drug side effects they have experienced. 