What Does Chkdsk Do Really? 

Here's what chkdsk actually does:
1. Fixes file system errors (NTFS, FAT32, etc.)
2. Locates bad sectors in the hard drive.
3. Attempts to recover information before marking bad sectors.
4. After marking bad sectors, chkdsk prevents data from being store d in them.
Useful commands for Windows Terminal, Powershell or Command prompt,
chkdsk /? -This shows all chkdsk command parameters
chkdsk /f - Fixes errors on the disk
chkdsk /r - Locates bad sectors and recovers readable information