Prospective patients will be tested for matching with an HIV-negative donor (family member) and will undergo a medical history, physical examination and several tests (e.g., breathing tests, X-rays, etc.) to determine eligibility for the study. Study participants will then undergo apheresis to collect white blood cells called lymphocytes. Stem cells will be collected from the donor. Half the donated cells will have the HIV-resistant gene inserted; the other half will have a "control" gene inserted. Additional stem cells collected a second day will not be manipulated. All the donor cells will be frozen until transplantation.