My :G drive wont work! HELP!?

this hard drive is pluged in via usb cable and it wont work for me. it would switch on and auto play and then switch off until i kept plugging in and unplugging usb plugs. it has all my downloads on there so it may have a few virus' but ive scanned abillion times so i dont think so. tried rebooting tried swapping usb ports tried blowing the dust out of the ports but it wont work!!! grrrr. please help! thanx to everyone that helps