Partition is not visible (disk is attached, but you don't see a drive letter in file explorer)
Partition is not accessible (volume is visible, but Operating System pops up an error when accessing it)
Partition is not bootable (Operating System fails to start properly)
The most common causes of partition issues:
Physical damage of critical sectors on a HDD (known as unreadable or 'bad sectors')
Loss of information due to an electrical failure or power surge
Accidental deletion of the logical drive/partition
Accidental formatting of the logical disk/partition
Damage of the MBR, Partition Table, Volume Boot Sectors by a software virus or malware
Improper use or execution failures of backup/recovery software tools
When the volume is damaged it usually displays one of the following symptoms:
Original partition/drive is no longer visible to the Operating System (deleted, damaged, or overwritten)
Partition/Volume is visible but important files/folders are not visible (drive re-formatted or damaged)
In both cases partition recovery software must analyze the surface of the physical drive for residual logical data and organization clues in order to reconstruct the partition/drive parameters (such as the first sector number, cluster size, file system type, etc.).
After a user obtains an access to this virtual drive, he is able to re-create partition (recover partition information) or just to copy lost data to another drive (with use of a file recovery program).
Examples of low level partition damage and recovery procedures
We assume that you have some knowledge of a HDD and the File System's organization to be able to understand the data recovery terminology and examples above. If not, please read about Hardware and Disk Organization first.