This is on page 9 of the user manual available atSystem Requirements:
This hard drive is compatible with the operating systems
MS Windows XP / Vista / Windows 7 and Mac OS 10.x.
For the USB 3.0 operation an USB 3.0 interface card is needed. The hard disk is downwardly compatible with the previous USB standards.
Your PC’s hardware configuration as well as the operating system employed can influence the compatibility of the hard drive.
Power supply under USB 2.0: If your USB 3.0 hard disc is not recognized on your PC with a USB 2.0 connection, this could probably be caused by the power supply. In this case, please connect an USB hub with an external power supply.