There are four main types of hard drives available. There is USB, Firewire, SATA, and eSATA. Hard drives are also available as external and internal. You can find more information here: http://www.seagate.com/ww/v/index.jsp?locale=en-US&name=hard-drive-basics-dn&vgnextoid=2df42bb581b51210VgnVCM1000001a48090aRCRD
