I. To establish the maximum tolerated dose (MTD) of a large field image-guided IMRT, using helical tomotherapy, when given in combination with IV busulfan and VP-16 as a preparative regimen for allogeneic hematopoietic stem cell transplantation (HSCT) from an HLA-identical sibling in patients with advanced myeloid malignancies. (Phase I) II. To describe the toxicities at each dose level studied. (Phase I) III. To estimate the radiation doses to the whole body, normal organs, and bone marrow through serial imaging studies following the administration of IMRT. (Phase I) IV. To estimate the overall survival probability, disease-free survival probability, and relapse rate associated with this preparative regimen. (Phase II) V. To characterize the treatment related mortality and toxicity profile (early/late) associated with this regimen. (Phase II) VI. To descriptively compare the outcomes of patients treated on this protocol to a comparable patient population conditioned with whole-body radiotherapy. (Phase II)