A thumb drive which my daughter was using to transfer work from the windows xp desktop she was using at school to her windows xp laptop she uses at home is no longer being recognized by either machine nor four others I've tried including one macintosh. I've tried using data recovery software but it depnds on initailly being able to recognize the device, then proceeds to recover corrupted files. In this case, the device itself is no longer being recognized. The only response that the computer makes to the thumb drive being plugged into the usb port is "USB Device Not Recognized." Help!