Make sure that the USB Hard Drive has the power cable plugged in, then plug the USB cable into the side of the Mac. Give it a minute or so and it should appear on your desktop. CJC
not all usb drives need power cables as one of the 2 i have just has the one which i just plug into the usb port, computer sees it & either asks for the driver or loads its own depending on the operating system. the other usb drive i have has 2 cables that end with usb males( the 2nd cale is for power when not enough power is supplied through 1 usb port)
All external USB Hard Drive's should have an external power source because the USB port does not have enough power to power the drive. Plugging it into a Mac, you just need to plug in, and wait and it will display it on the desktop CJC
it depends on the motherboard whether it has enough power or not. my 6.4gig laptop drive in a powerdata usb 2 slim case normally plugs into 1 port but on some p1 type motherboards i have to plug into both port. drive comes in handy when saving a customer's information before blowing out their drive or putting updates to AVG or Lavasoft instead of downloading through dialup