I've been using my old ST500DM002 as a backup drive. It started making a crackling noise, and didn't show up on the drive list. I rebooted without luck, then powered down and started it up again.

The bootup insisted on disk-checking the backup drive, and it was temporarily available again.

Now the drive is completely inaccessible. I put it back in its old tower, tried booting it up, but it's undetectable on that as well.

Any suggestions?