The fail of hard disk
When the Spindle Motor does not activate.
When the Partition Table has been deleted.
Missing Operation System
Invalid Media Type
Deleted Data
Formatted
Overwriting
Low-Level Format
  Invalid Media Type
 
1.

In this case the Boot Record has been broken, and even if you boot your computer through the A: (FDD) it is impossible to start your computer.
   
2.

It can also fix it by Norton Disk Doctor.