Data-loss

Data-loss results from the fact that the direcotry entries and/or the FAT are deleted or contain incorrect information. The operating system works at an access to files as follows: Read data from directory entry -> Read data in the data area-> Read informationen from the FAT and repeat from next to last step until file is completely read. If the directory enties and/or the FAT are incorrect or deleted, the operating system can not read however any longer, although this is still in the data area. This is the reason why users think, their data is lost - in reality it is still available. Finding this data can be very complex however somtimes, since the entire drive has to be examined.

Data-loss of the content itself
Data is completely lost, if the content is damaged or overwritten (the file was not lost due to incorrect information in the FAT or the directory entries).

This could have the following causes:

1. The Hard disk/floppy disk is physically damaged
2. Viruses or something else destroyed the data
3. Writing other files to the disk has led to it, that some or all clusters of a file were changed. In this case only a part of the data can be recoverd.