another less expensive software based solution that has save my but a few times is spinrite. Even if your drive drops sectors that contained OS files/drivers, it can usually recover them and make the disk readable again. delete a partition by accident? no problem, it can usually rebuild them if you havent overwritten it yet.
A friend of my roomate gave his old computer to my roomate for his kid after a shop told him the drive was dead. I ran spinrite on the drive to see if we could still use the same drive, and to my surprise, I got the pleasure of calling the person back and asking them if they wanted their data off the old drive.
Not quite a king demi, but does the job most of the time.