Leo thinks that Disc Utility is seeing the USB interface, but may not be seeing the drive. Eric says it can check the drive and reports a volume error and won't mount. Leo says to take the drive out of the USB case, put it into a PC, then run SpinRite on it. Eric is also wondering if he should clone the drive before doing any of this. He can try, but cloning software isn’t persistent and may just give up. SpinRite is nondestructive anyway.