HKDSK (short for Checkdisk) is a command on computers running DOS, OS/2 and Microsoft Windows operating systems that displays the file system integrity status of hard disks and floppy disk and can fix logical file system errors.
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Disk Check happens whenever something happens that shouldnt happen on your System.
It is a normal Windows process.
Say the "Explorer.exe" process were to stop working and you cant get it back up, so you have to do a hard reboot. DskChk opens and prevents any corruption.
If you don't shut down properly, the hard drive isn't marked as being shut down properly, so the computer will check it for damage. That check is a disk check.
Disk check runs when your computer shuts down unexpectedly, its a built in Windows feature. It checks you disk (your hard drive) for errors and corruption. No worries, all is fine.