External hard drives need USB 2.0
A few years ago the speed of USB ports moved from roughly 12mbps to 480mbps. In order to get the new speed, you much have USB 2.0 ports.
USB 2.0 comes standard on all computers on the shelf today, but if your computer is three years old or older, you may need to add USB 2.0 ports to your computer if you are running a high speed device.
Important devices to run on USB 2.0 ports are MP3 playes – like the iPod, external hard drives, or large flash drives packed with a lot of information. Scanners also work much faster on USB 2.0 ports.
In order to reach the full benefits of USB 2.0 both the device and the port much be designed for USB 2.0.