Busulfan is only given once daily by IV in this study, which is also not approved by the FDA. Patients in this study will go through standard procedures for their disease like medical history, physical exam, blood tests, Multi Gated Acquisition Scan (MUGA) scan or echocardiogram, bone marrow aspirate or biopsy, and lung functions test. Patients will be asked to donate additional blood and bone marrow for this study and for potential future research on their blood related to this study. Because of the normal procedures for HPC transplants patients in this study will be hospitalized for 4 to 6 weeks or longer and will make frequent trips to the clinic to visit the study doctor for supervision for at least one year. Each patient will also have to have a central venous catheter inserted into a large vein above the heart. This is used to give the drugs and to take blood samples.