In the case of a crashed hard drive, there are some things you should avoid. Do not shake the drive. Don't jar it. Don't hit it. This can only make matters worse. In the past, freezing the hard drive was tried, but this should be avoided at all costs. Running scan disk is not a good idea. Neither is attempting to reformat the drive or changing partition parameters.
So what should you do? There are a few things you can try yourself. Try connecting it as 'slave" on another computer. If this works then you will be able to see the drive, it's contents, and possible problems. But ONLY do this if your drive is NOT making unusual noises such as clicking, grinding, whining, etc.