I have dealt with many hard drive failures in the past, and most of the time it was the result of bad sectors. Other times it was a complete failure where the hard drive wouldn’t even power up. In the latter instance there isn’t much you can do to retrieve your data.
As for bad sectors, you may still be able to retrieve your data, if you have the right tool. It is difficult to copy data from a damaged hard drive, especially in Windows since it would usually stop the copy when it encounters a bad sector. Recently, I managed to retrieve over 5GB of data from a hard drive with many bad sectors, and in this post I’ll tell you how I did it.