CHKDSK errors occur whenever Windows detects a problem with the file system on your hard disk, and tries to automatically repair it by running the CHKDSK application. Although CHKDSK can fix such errors, Windows also frequently misdiagnose the cause of the problem, and can actually makes things worse.

What causes CHKDSK errors?

Many things can trigger Windows to launch the CHKDSK to scan and repair the hard drive. Among the most common are logical errors in the file system, bad sectors on the hard disk, lost clusters, cross-linked files, and directory errors. Viruses can also cause CHKDSK errors, in particular the notorious Zobot virus. All these things can lead to problems with Internet Explorer, files being corrupted or lost, and make the PC lag or even freeze up.

However, for the average PC user, the most frequent reason Windows launches CHKDSK is if the computer was shut down incorrectly. This can be caused by power blackouts, the computer freezing or crashing, or even if the user simply turns off the PC without shutting Windows down first. Similarly, when any program (such as MS Word or Photoshop) or is aborted instead of being closed out by the user, it can cause data clusters to become lost. In the case of improper shutdowns, Windows automatically launches CHKDSK the next time the PC is turned on.

Windows does this to scan the hard disk for corrupted sectors or file system errors so it can automatically fix them before the operating system boots up. Unfortunately, this automation can be a problem in cases where running CHKDSK makes things worse.

How can CHKDSK make problems worse?

As long as hard disk errors like lost clusters and bad sectors really are being caused by problems with the file system, CHKDSK works fine. The catch is that such errors are identical symptoms of other, more serious problems with the computer, such as a physically damaged hard drive. In such cases, Windows misdiagnoses the cause of the problem and runs CHKDSK anyway. Not only are these problems that CHKDSK does not and cannot fix, but it can also make the problem worse while trying to apply the wrong solution. Imagine a plumber trying to fix a leak that is actually being caused, not by the pipes, but by a hole in the roof.

In the process of CHKDSK attempting unsuccessfully to correctly rewrite a non-existent file system problem on a physically damaged sector of the hard disk, the data contained in that sector may become fragmented, corrupted, and irreparable. Consequently, files that may have been recoverable are now hopelessly scrambled. If those files are crucial operating system files, the PC can be damaged beyond repair, with the only repair option left being a complete reinstallation of Windows.

How can I stop CHKDSK from running automatically?

In Windows 95 and 98, an older version of CHKDSK (called Scandisk) will search the hard disk for problems and then ask you if you want to repair any errors found. As it is the repair process that can corrupt data on damaged hard drives, simply selecting “no” will avoid any problems. In Windows 2000/XP/Vista, however, CHKDSK will automatically try to repair any errors found without asking you first. To abort CHKDSK, simply press the ESC key within 10 seconds after it starts running. From there, your PC will continue to boot into Windows. Once in, you can back up you important files to another media (such as CD or DVD) before trying to fix the hard disk problems.

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