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Can CHKDSK Corrupt Files?

The harm has likely already happened.

If CHKDSK freezes when you run it, you may have a problem with your files or hard disk, but CHKDSK didn't cause them.
Looking at a Hard Disk.
Question: I recently did a CHKDSK scan on two hard drives with video files. The first scanned with no options checked. It did not show any details of progress except the progress bar. It got to the end and then froze (although the computer did not freeze), and the only way to exit it was to shut down the computer or reset. Do you think any of my video files got corrupted or changed in any way? With the other hard drive, I scanned four times without errors. On the fifth time, I scanned it on another computer and it said that it had a file system error. Needless to say, I did not fix that. I don’t know if one of the four times before I checked any options, but I’m thinking I had nothing clicked. Is it possible that my video files on the hard drive got corrupted or changed in any way even if I had clicked one or both of the options?

You may have problems with your video files, but it’s not because of CHKDSK. With no options selected, the CHKDSK utility simply reports the current status of your hard drive.

But there are a couple of interesting things about CHKDSK that I think are worth reviewing here.

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CHKDSK and file corruption

CHKDSK does not cause file corruption, but it can expose pre-existing problems on a hard disk. The best prevention is to back up regularly so that when, not if, problems occur, you won’t lose any data and will be minimally inconvenienced.

What CHKDSK does

CHKDSK makes sure that the directory (the listing of files on the disk) refers to the correct files in their correct places. CHKDSK verifies that all the pieces are there, the data is structured properly, and everything Windows needs to maintain the file system is in proper order.

When CHKDSK discovers that one of these things isn’t right, it reports that as an error.

CHKDSK with no options checked is read-only

If you don’t specify any options other than the drive to be checked, CHKDSK doesn’t try to fix anything. It just reports on the status of the information currently stored on the drive.

If it reports an error, that’s because the error was already there.

If it freezes, it’s because there’s an error it can’t recover from. Once again, that error was there before you ran CHKDSK.

What CHKDSK does not do

That your system froze is interesting but not uncommon. The freeze is usually because CHKDSK could not recover from an error that it found in the file system. If CHKDSK freezes, your computer’s hard disk may have a problem.

Before we go any further, I need to reiterate: the problem was already there before you ran CHKDSK. All CHKDSK did was report (or in this case, hang as a result of) an error on the hard disk. It didn’t mess up your video files.

Something was already wrong with them.

Repairing files

CHKDSK will attempt to repair things:

  • If you specify the /R or /F options when you are running CHKDSK from the command line.
  • If it finds errors when you run “Error checking” via Windows File Explorer.

But again, CHKDSK is only trying to repair damage that has already been done. CHKDSK will force the file system to be in a correct and coherent state, and that may cause errors to become visible. This is only because damage has already occurred.

Where errors come from

File-system errors can come from many different places. The most common reasons include not shutting down Windows properly, experiencing a crash, or having the power go off while the system is running. It’s also possible that the hard disk itself could be failing.

The reality is that errors happen. Hard disks fail. It’s the way computers work.

Do this

The only real way to prevent this from being a serious issue is to back up regularly so if (or really when) something happens to your files (whether they’re video files, data files, or even the files comprising Windows itself), you’re protected. You have backup copies and can restore them to the replacement hard drive, the fixed software, or whatever.

But don’t blame file problems on CHKDSK.

It’s just trying to help.

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9 comments on “Can CHKDSK Corrupt Files?”

  1. Gone are the days of Norton Disk Doctor, a suite of tools that would analyze and attempt to fix just about anything on your PC, all from a nice graphical user interface. I can’t seem to find a modern day equivalent (and no, Norton Utilities doesn’t even come close to comparing). Any insight on a solid, non-invasive, easy-to-use tool that can analyze and remedy disk problems would be appreciated. I want something I can direct my mom to use.

    • Reid,
      Unfortunately I think that computers are just too complex for any program to automatically repair like that. A better idea would be to set her up with an incremental backup system. Then you can at least restore to a previous point when things worked. In the end, that’s the only reliable setup.

  2. Some years ago I was doingsome “housekeeping” on the computer, and deleted some files that I no longer needed. Then I tried to delete the folder and all its sub-folders, but found there was just one folder right at the end of a long chain (all legit) which I simply could not delete. By going in to DOS and fiddling around, I eventually managed to delete the entire chain, right back to the root directory. Fine. Just what I wanted.

    But what (I deduce) had happened was that that folder had been cross-linked. WHen I ran CHKDSK it found an error, and when I told it to fix it…. YES ! It converted every single file in my “My Pictures” folder, and produced seventy thousand different files in seven different folders of 10,000 files each.

    I still have them – this was all on an add-on hard disk, that I have not written to since. Now and again, when the mood takes me, I have go to see if I can retrieve any of them. So far, not a single one have I recovered….

  3. Man system refused to shutdown yesterday and I had to kill the power. After restart the system scanned using CHKDSK. It detected 4 unreadable segments

    Unreadable Segment 6000062-66

    I have noticed using Process Explorer that the system Idle Process is actually using high CPU usage which freezes Windows temporarily. I know this isn’t actually a process but before the problem the System Idle Process ran at low cpu usage.

    (I’ve decided to backup and make an image of my machine due to a prediction that my hard-drive is on its way out)

    Any ideas?

    • If your system is freezing it’s NOT NOT NOT because of the system idle process. It’s not a process, but just an indicator that the CPU is doing nothing – i.e. it’s idle. Something else – quite possibly the hard drive from the sound of it – could be causing your system to freeze without impacting the CPU.

  4. Well honestly, Chkdsk CAN harm your files, as some scans can leave files corrupted afterwards or even delete entire hard drives of data (I experienced this back in 2005, June 1st).
    And back in April this year, several bunches of files were either deleted or left corrupted and unviewable following a sudden boot-up scan (on a large and new 2TB HDD that was becoming unstable being connected inside the PC to my GA-970A-DS3, but did OK when I put it in a USB box).

    Now I wonder what on earth to do with these corrupted files. Tons of PNG’s. They still have the thumbnails when present in that folder. And if viewing them in HEX editors, they don’t consist of 0’s or ‘NUL’ if viewed in Notepad++. But I had no luck trying to restore them with any recovery software that I desperately tried scouring for.
    Not even with CHKDSK itself, which said it was fixing lots of damaged clusters in the very files that are corrupted, after I ran it with a “chkdsk (drive): /f /r” command – and yet no result. Is there a way to fix these from my description?

  5. If CHKDSK or any other program freezes, it’s rarely necessary to restart your machine. You can shut down any misbehaving (or behaving) program using the Task Manager. There are a few ways to open the Task Manager. For me, the simplest is to hold down SHIFT and CTRL and press ESC.

  6. I really REALLY miss the days when I could get on the phone with Peter Norton when I had a hard drive problem and he would explain how to make Norton Disk Doctor solve the problem – quite often ending up with the next version having that feature brought out in the interface – or the non-existing feature added. At the time I worked for the largest seller of hard drives for IBM computers in Canada – back when the IBM PC was only available with either 1 or 2 floppy drives, and a 5MB hard drive was HEAVEN!!!! – and cost about twice as much as the base computer. Back in the days of green monochrome monitors.


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