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How to Scan & Fix Hard Drives with CHKDSK in Windows 10

CHKDSK (pronounced “Check Disk”) is a very useful and vital tool for monitoring your disk drive health. This tool uses a multipass scan of a drive to verify that its soundness and functionality are intact. Using CHKDSK to ensure your drives are running correctly is a great way to speed up Windows 10 [1], and we suggest you use the tool every few months to keep your drives safe and healthy.

In this article, we’ll go over what CHKDSK is, how it works, and how you can use it to repair your hard drive in Windows 10.

How CHKDSK Works

CHKDSK starts by scanning the file system on the disk drive and analyzing the integrity of the files, file system, and file metadata on the drive.

When CHKDSK finds logical file system errors, it fixes them in place, saving the data that is on the disk so that nothing is lost. Logical file system errors are things like corrupted entries in the drive’s master file table (MFT), a table that tells the drive how files are connected in the murky labyrinths of the drive’s hardware.

CHKDSK also fixes misaligned time stamps, file size data, and security flags on files on the drive. CHKDSK can then conduct a complete scan of the drive, accessing and testing every sector of the hardware. Hard drives are divided into logical sectors, defined areas of the drive where a certain defined quantity of data will be stored.

Sectors can develop soft errors, in which case data has been written incorrectly to the magnetic medium, or hard errors, which are cases when the drive itself has an actual physical defect in the area designated as a sector. CHKDSK fixes soft errors by rewriting the faulty data and resolves hard errors by marking that section of the disk as being damaged and ‘out of bounds’ for future use.

Because CHKDSK has been updated and upgraded repeatedly with each new generation of storage hardware, the program continues to work correctly to analyze and repair hard drives of any sort. The same process that used to be executed to analyze a floppy disk holding 160K, can today be executed to analyze an SSD holding 15 terabytes.

Running CHKDSK on Windows 10

Although there are several different ways that you can invoke CHKDSK on a Windows 10 machine, by far the most common and ordinary place to run the utility is via a command prompt known as the Windows PowerShell.

However, because CHKDSK talks directly to drive hardware, it requires a special level of operating system permission known as administrative privileges. This just means that CHKDSK is allowed to run as though it was the account that is in charge of the computer.

To launch the Windows PowerShell, press  the Windows Key + X. This brings up the power users menu in the start menu area, where you will see several options. You can release the Windows Key + X combination and type the A key (short for Admin) to launch the Windows PowerShell in administrative privilege mode. You can also simply move the mouse to the Windows PowerShell (Admin) line and click to launch the shell that way.

The next screen to appear is a User Account Control (UAC) window which will ask for permission to launch the Windows Command Processor and let it make changes to the PC. Select “Yes.”

The Windows PowerShell will now launch a familiar black and white box with a text command-line interface. The most basic way to invoke CHKDSK is simply to type the name of the program “chkdsk”, followed by a space, then the letter of the drive you wish to examine or repair.

In our case, it’s internal drive “C:”, so the command would be “chkdsk c:”

This basic invocation of CHKDSK will scan the disk and display status information, but it will not fix any errors that are encountered.

To run CHKDSK in a mode where it will actually fix problems that it encounters, you need to add several parameters. In a Windows PowerShell program, parameters are additional commands added to the end of the program name, with “/” characters before each parameter. In this case, to get CHKDSK to do a full scan and repair pass, we would want to type “chkdsk c: /f /r /x”.

The “/f” parameter instructs CHKDSK to fix any errors that it discovers during its scan. The “/r” parameter tells CHKDSK to locate any bad sectors and recover any readable information it finds there. The “/x” parameter tells CHKDSK to dismount the drive (take it offline from the operating system) before the process begins.

Additional CHKDSK Parameters

CHKDSK has a large library of optional parameters that you can use to modify the program’s behavior.

To summarize, the full command that should be typed into the Command Prompt is:

chkdsk [Drive:] [parameters]

In our example, it’s:

chkdsk C: /f /r /x

Using CHKDSK on a Boot Drive

A boot drive is the partition of your hard drive that the computer starts up from. Boot partitions are special in many ways, and one of those ways is that they require special handling for CHKDSK to be able to deal with them.

CHKDSK needs to be able to lock any boot drive it scans, meaning that it cannot examine the system’s boot drive if the computer is in use. If your target drive is an external or non-boot internal disk, the CHKDSK process will begin as soon as we enter the command above.

If, however, the target drive is a boot disk, the system will ask you if you’d like to run the command before the next boot. Type “yes” (or “y”), restart the computer, and the command will run before the operating system loads, allowing it to gain full access to the disk.

A CHKDSK command can take a long time to execute, especially when performed on larger drives. Once it’s done, however, it will present a summary of results including total disk space, byte allocation, and, most importantly, any errors that were found and corrected.

CHKDSK In Previous Editions of Windows

The CHKDSK command is available in all versions of Windows, so users running on Windows 7, 8, or XP can also perform the steps above to initiate a scan of their hard drive.

In the case of older versions of Windows, users can get to the Command Prompt [2] by going to Start > Run and typing “cmd”. Once the Command Prompt result is displayed, right-click on it and select “Run as Administrator” to grant the program the necessary privileges to execute CHKDSK successfully.

One warning note: if you use CHKDSK on an older hard drive, you may find that your hard drive space was significantly reduced after running the command. This result is due to a failing hard drive [3], as one of the crucial functions that CHKDSK performs is to identify and block bad sectors on the drive.

A few bad sectors on an old drive will typically go unnoticed to the user, but if the drive is failing or has serious problems, you could have huge numbers of bad sectors that, when mapped and blocked by CHKDSK, appear to “steal” significant portions of your hard drive’s capacity.

Other Ways to Launch CHKDSK

If you dislike using the command prompt, there are other ways to invoke CHKDSK on your system. Perhaps the easiest is directly through the Windows Explorer.

Open a Windows File Explorer window and navigate to the drive you wish to check.

Right-click on the icon for your hard drive and select Properties.

Select the Tools tab and click on “Check” to launch CHKDSK with standard parameters.

Final Thoughts

CHKDSK is a very powerful tool for scanning and fixing hard drives on Windows 10 computers. By following the steps outlined above, you can use this helpful function to optimize your PC’s performance.