RATIONALE: Although used primarily to treat malignant disorders of the blood, allogeneic stem cell transplantation can also cure a variety of non-cancerous, inherited or acquired disorders of the blood. Unfortunately, the conventional approach to allogeneic stem cell transplantation is a risky procedure. For some non-cancerous conditions, the risks of this procedure outweigh the potential benefits. This protocol is designed to test a new approach to allogeneic stem cell transplantation. It is hoped that this approach will be better suited for patients with non-cancerous blood and bone marrow disorders.