Hard drives, other than their size, they haven't really changed much over the years. There have always been two major formats; IDE and SCSI. While SCSI, primarily geared towards the Enterprise district, for both its speed and expansion capabilities has always been traditionally the more expensive. The slower, inexpensive IDE has taken a strangle hold on personal computer market. While IDE is traditionally slower than SCSI, increases in both cache size and RPM speeds coupled with the massive disk size and lower price have kept IDE drives popular for the average user.