The process in which a relatively unspecialized cell acquires specialized features of a hematopoietic stem cell. A stem cell is a cell that retains the ability to divide and proliferate throughout life to provide progenitor cells that can differentiate into specialized cells. [ GOC:dph GOC:BHF GOC:bf GOC:rl http://www.ncbi.nlm.nih.gov/pubmed/15378083 ]