Combination Chemotherapy and Antithymocyte Globulin in Reducing Graft-Versus-Host Disease in Patients Undergoing Donor Stem Cell Transplantation For Myelodysplastic Syndrome or Myeloproliferative Disorder

RATIONALE: Combining antithymocyte globulin with combination chemotherapy before donor peripheral stem cell transplantation may reduce the chance of developing graft-versus-host disease following transplantation. PURPOSE: Phase I/II trial to study the effectiveness of combining antithymocyte globulin with busulfan and cyclophosphamide in reducing graft-versus-host disease in patients who are undergoing donor stem cell transplantation for myelodysplastic syndrome or other myeloproliferative disorder.