If you have important data, get it off that drive. If you want to play with it, then feel free.
My advice, stemming from almost two decades of hard drive experience, is to scrap that drive. Modern recording media on hard drives is, shall we say, brittle. Once it starts to go bad, a complete failure is not far behind.
I have used HDD Regenerator to stabilize a drive with important data on it when a customer did not want to pay the $500 - $2500 a professional clean-room recovery outfit wanted to charge. I did make a handsome profit due to the time involved tying up my machinery (it took several days to run, during which time, at any given second, the drive could have just gone tits-up,) then recovering the data and manually sorting it for the customer.
As Piru said, new drives are dirt cheap. I would go so far as to say obscenely cheap. The fact that the drive is spinning down shows that there is something more ominous going on with the drive.
Is it worth playing with? Maybe academically. But unlike SCSI hard drives of the past, once a hard drive develops bad spots and erratic behavior, it is time to relegate that drive to non-critical use.
My second rule of data recovery is to not play with live data. Once you have a safe copy, then you can play all you want.
I have done this many times before, given back a customer his or her data, then asked permission to work with the drive on my own time, ensuring that it will be wiped as much as possible before disposal, or destroyed outright if requested. (There is an outfit in Georgia that grinds and burns the things. They even provide the shipping material, and chain-of-custody and destruction affidavits.)
