In Scan.co.uk's 'Today only' deals, the "640GB Dane-Elec SoMobile+" is only £41.99, with Free delivery for members of Avforum!.
(Full title: 640GB Dane-Elec SoMobile+ SO-MB4640 USB2 2.5" External HDD Bus Powered PC/MAC)
Go to the 'Today only' special offer page, and it is under 'storage', remember to click the green Buy button to get it at this price.
So Mobile + is an external Plug&Play hard disk drive. You will connect it easily to your computer with the USB cable (included).
It will allow you to increase your storage capacity and synchronize automatically a backup of your data (OTB function).
With PC Clone EX Lite Software
Fast & Light
Plug and Play