this really sounds like a dead drive then.
You might try to re-flash the firmware on plain DOS. Dell offers DOS flashers for TS-L632H, which come with their Vostro 1500 notebook series. Please do only extract the flasher and use it with the firmware (maybe an older version) for your own drive.
P.S.: If your notebook is still under warranty, then contact Dell support for advice.
Edit: Locoeng was faster with that