This is a randomized trial for patients undergoing hematopoietic progenitor cell transplantation (HPCT) from an unrelated donor. Approximately 50% of the patients enrolled will receive Thymoglobulin® as part of the preparative regimen prior to HPCT. The other 50% of the patients enrolled will receive a standard preparative regimen. Thymoglobulin is known to suppress the types of cells that can cause a transplant complication known as "chronic graft versus host disease (cGVHD)". The goal of this trial is to find out if adding Thymoglobulin to the preparative regimen will result in a decrease in cGVHD.