Problem in detecting hard disk in Seagate Expansion Portable Drive?

I have been using my Seagate Expansion Portable Drive SRD00F1 external hard disk for 9 months now. But now suddenly the computer has stopped detecting the hard disk. When I connect it to the 3.0 USB port the detection sound comes and the 'Safely remove your hard disk' icon also displays but after 5 sec. hard disk automatically ejects. When device is left connected for 15 min. or so Windows 8 pops up an alert message to repair the device, but the repair just stops proceeding after 30% or so. I have tried restarting the windows, Connecting to 2.0 USB port, thoroughly checking the tight connections. I have also checked in 'Disk management' and 'Device Manager' but device is not detected there as well. I tried to search for driver to manually install it, but it is not available on net.