Usb for external won't read on my computer

Hello,
i bought a 1Tb Comstar external hard drive. unfortunately the USB part in the drive snapped off so I sent it back to the company. They fixed it and sent it back to me. Now the USB cable for it wont even read on my computer. I have the home premium package for Vista. and on top of that I have files on my computer i can't backup because my disk drive is opening and closing constantly on it's own. help me out. My disk drive won't even read anything I don't know what to do I can't lose these files. help me figure out another way to back them up. please.