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
  Deleted Data
 
1.

When not saved after deleting files you usually can recover your files by the command UNDELETE.

   
2.

If you have used you computer for a long time after deleting, and saved another program or overwritted, you replaced the space where the original data was in most of these cases it is difficult to recover your data.

   
3. It is very important to stop whatever work when you have deleted a data you really need.
   
4.

Recovery success rate: 57%