First, dont go to a data recovery service or it'll costs you LOTS of money. (worked in one of those shops before) What they do is that your hd dies mainly because or electronics. So most of the time, they have to find a identical hd, bust out your disks and put them into the new hd. So its a lot of work and those companies charges big time. I would say if no business or no major school project depends of this hard drive, consider letting it die. Or at least find a place where they give estimates before doing anything. Software doesnt give any results usually; they're good for corrupt files under the windows environnement, but not for the hardware side of the issue.
You tried the usb external way, but did you plug it into another computer?
Is this your primary hard drive in your actual computer? If so, find another working computer and try putting it in slave and see if it can be detected in slave. It happened to me twice and I was able to detect the HD once. So its a 50/50.
Let me know what happens and maybe i'll think of something else. Maybe I can call my ex workers too to see how they would approach your situation.