Check Disk scans your hard drive for errors and can fix some of them automatically

Check Disk (often called "chkdsk") is a Windows tool that looks for problems on your hard drive — things like corrupted files, lost clusters of data, and bad sectors. When you run it, the tool reads through your drive's file system and reports what it finds. Depending on how you run it, it can also attempt to repair some of those problems on the spot.

You do not need to be a technician to use it. The tool is built into Windows and runs from your command line or through your settings. Most people run Check Disk when their computer is acting slow, when files go missing, or when Windows suggests it during startup.

Key Takeaways

  • Check Disk scans your hard drive for file system errors and can repair some of them, but it cannot recover deleted files or fix hardware failure.
  • You can run Check Disk from the command prompt with administrator rights, or through Settings on Windows 10 and 11.
  • Running Check Disk with repair options requires your drive to be unmounted, which usually means scheduling it to run at the next restart.
  • Check Disk takes longer on larger drives and older computers, sometimes 30 minutes to several hours depending on drive size and damage.
  • If Check Disk reports bad sectors repeatedly, your hard drive may be failing and you should back up your data soon.

How to run Check Disk from the command prompt

Open the Start menu and type "Command Prompt". Right-click on "Command Prompt" and select "Run as administrator". This gives the tool the permissions it needs to scan your drive.

At the command prompt, type chkdsk C: (replacing C with your drive letter if you want to scan a different drive). Press Enter. This version only scans and reports problems — it does not fix anything. You will see a list of any errors found.

To let Check Disk repair errors, type chkdsk C: /F instead. The /F flag tells it to fix problems. Windows will tell you it cannot run while the drive is in use and will ask if you want to schedule it for the next restart. Type Y and restart your computer. Check Disk will run before Windows fully loads, which can take a while.

Running Check Disk through Windows Settings

On Windows 10 and 11, you can also reach Check Disk through Settings. Open Settings, go to System, then Storage. Scroll down and click "Repair storage sense" or look for a "Scan" or "Check" option under your drive. This opens a simpler interface that lets you schedule a scan without typing commands.

The Settings route is slower than the command prompt and gives you less control over which flags run. If you are comfortable with the command line, the prompt method is faster. If you prefer clicking through menus, Settings works fine.

What Check Disk actually fixes and what it cannot

Check Disk can repair file system errors — problems with how Windows organizes and tracks files on your drive. It can also mark bad sectors (small areas of the drive that no longer work) so Windows stops trying to use them. If a file is fragmented across a bad sector, Check Disk may move it or mark it as corrupted.

Check Disk cannot recover files you have deleted. It cannot fix a drive that is physically failing. It cannot restore files that were overwritten. If your hard drive is making clicking sounds or your computer is freezing constantly, Check Disk will not solve the problem — those are signs of hardware failure, and you need to back up your data and replace the drive.

How long Check Disk takes and what to expect

A scan-only run (without the /F flag) usually takes 10 to 30 minutes on a modern computer with a 1 TB drive. A repair run can take 30 minutes to several hours, depending on how many errors it finds and how large your drive is. Older computers and larger drives take longer.

During a repair run at startup, you will see a black screen with white text showing progress. Do not turn off your computer or unplug it. Let it finish, even if it seems stuck. If it has not moved in over an hour, restart and try again — sometimes Check Disk gets stuck on a very damaged drive.

When to run Check Disk and when to skip it

Run Check Disk if your computer is running slowly, if Windows suggests it during startup, if you see error messages about corrupted files, or if a specific drive is acting unreliable. You can also run it as routine maintenance every few months on an older computer.

Skip Check Disk if your drive is making hardware noises (clicking, beeping, grinding). Skip it if you have already lost important files and have not backed them up yet — running repairs might overwrite data you could recover with professional tools. Skip it if your computer is brand new and working fine; there is no benefit to running it on a healthy drive.

What to do if Check Disk finds a lot of errors

If Check Disk reports many errors or the same errors repeatedly after repair, your hard drive is likely failing. Back up your important files to an external drive or cloud storage as soon as possible. You do not need to replace the drive when ready, but plan to do so within weeks rather than months.

If Check Disk finds errors on an external drive or USB stick, the same rule applies: back up what you need and consider replacing the device. External drives fail the same way internal ones do, and repeated errors are a warning sign.

Frequently Asked Questions

Will Check Disk delete my files?

Check Disk does not intentionally delete files. If a file is corrupted or stored on a bad sector, Check Disk may move it to a "lost and found" folder or mark it as unreadable. You can usually recover these files if they are important, but they may be partially damaged.

Can I use my computer while Check Disk is running?

If you run Check Disk with the /F flag, Windows will not let you use the drive while it scans. You must schedule it for the next restart. If you run it without /F (scan only), you can use your computer, but performance will be slower.

What does "bad sector" mean?

A bad sector is a small area of your hard drive that no longer stores data reliably. It can happen from age, physical damage, or manufacturing defects. Check Disk marks these areas so Windows avoids them, but if you have many bad sectors, your drive is aging and should be replaced soon.

Do I need to run Check Disk on an SSD?

SSDs (solid-state drives) use different technology than traditional hard drives and rarely develop the kind of errors Check Disk fixes. You can run it if Windows suggests it, but it is less common and usually less necessary on SSDs.

What if Check Disk gets stuck or freezes?

If Check Disk has not moved in over an hour, restart your computer. Try running it again, but this time without the /F flag to see if it can at least scan. If it freezes repeatedly, your drive may have serious hardware problems and you should back up your data and consider replacement.