Desktop PC with Windows 8. My Maxtor 500GB external hard drive has been working perfectly for maybe 4 or 5 years since I bought it. Suddenly it's no longer visible in Computer. The power is on as indicated by the plug in the wall, the other end in the external hard drive and the green light on the hard drive case. The USB connection must be OK because I've tried other peripherals on the same one. Is there anything I can do or should I just buy a new one?