The Y shaped USB cable can be used if your G-Drive Mini is connected to your computer via the USB port but is unable to mount causing a clicking sound every second or so.
This happens when the onboard USB bus is unable to provide enough power to the G-Drive Mini. In these cases, it sometimes helps to use the Y shaped cable to draw more power from a second USB port.
In some rare cases, computers still are unable to provide adequate amount of power to get the external drive to mount. In these cases, an optional power adapter will need to be used. This adapter can be purchased from G-Technology using the following link: http://g-technology.com/Products/Accessories.cfm