o lawd
If you plug in the hard drive does the motor spin up*? Does it show up as a drive? When my 4.3GB drive died a while ago it didn't completely fail. It stayed running for long enough for me to get my porn data off of it. Whenever it would crash and refuse to work I would shut down, let it cool down, and try again.
*This doesn't sound safe but it really doesn't hurt anything. The best way to check that is to shut your system down, plug the drive into a free power connector (the ATA/SATA data cable isn't necessary), hold the drive in your hands by the sides (don't touch the circuit board!), and turn on the system. You should be able to feel it when it spins up. Alternative, you should be able to hear the drive spinning if you put your ear near it.
If it is completely DEAD dead (to the point where it won't even power on), I think your only choice would unfortunately be to send it to a professional, which is generally very expensive.