CHKDSK: How to Check Your Hard Drive for Errors and Fix Them

CHKDSK (pronounced "check disk") is a built-in Windows utility that scans your hard drive or solid-state drive for errors and, in most cases, repairs them automatically. Hard drives can develop problems over time — small corrupted sections, file system inconsistencies, or physical "bad sectors" where data cannot be reliably stored. Running CHKDSK helps catch and address these issues before they cause data loss or system crashes.

You should consider running CHKDSK if your computer is freezing or crashing frequently, if programs take an unusually long time to open, if you hear unusual clicking or grinding sounds from your hard drive (a traditional spinning hard drive, not a solid-state drive), or if Windows reports file system errors. It is also a good idea to run it on an older PC as a routine check every year or two.

CHKDSK can be run in read-only mode (it just scans and reports problems without fixing them) or in repair mode (it finds and fixes issues). For most situations, repair mode is what you want.

If CHKDSK finds a bad sector — an area of the drive where data cannot be written reliably — it marks that area so Windows avoids using it in the future. While this helps prevent further data loss, it is a warning sign that your hard drive may be aging and could fail completely in the future. Back up your files immediately if CHKDSK reports bad sectors.

Running CHKDSK on your main C: drive while Windows is running requires a restart — the check runs before Windows fully loads. CHKDSK on secondary drives (like a USB drive or a second internal drive) can run without a restart.