Why won't CHKDSK (Scandisk) for Windows XP fix file errors while Windows is loaded?

Dennis Faas's picture

My friend Abba from California called me on the phone this morning after he received yesterday's issue of the Gazette which talked about Disk Imaging and Partitioning.

Abba asked me why Windows XP didn't come with Scandisk and wondered why something so important such as Scandisk isn't easily accessible on the Desktop.

I told Abba Windows XP doesn't use Scandisk anymore and now uses a program called CHKDSK. By the way, CHKDSK actually means "check disk."

To use CHKDSK on Windows XP and scan your hard drive for errors usually caused by an improper shutdown:

  • Double-click My Computer
  • Right-click a hard drive (C drive, for example)
  • Select Properties from the Pop Up Menu
  • Go to the Tools Tab
  • Click on the Check Now button
  • Choose Automatically Fix File System Errors

Windows will more than likely ask you to reboot the computer.

Why does the computer need to reboot to allow CHKDSK to complete?

CHKDSK requires that you reboot your computer so that the hard drive can be dismounted from the operating system. "Dismounting a volume", as it is referred to, essentially closes all files that are in use by the operating system (or other running programs) so that it can be checked and cleaned properly.

" But... Windows 9x let's me run Scandisk while Windows is still running! "

Of course it does. And have you ever noticed that Scandisk sometimes has to stop and then restart multiple times, as does Defrag?

The reason: there are open files on your hard drive as it is being checked for errors, and that causes Scandisk or Defrag to restart repeatedly. That's why Windows XP tells you to reboot the machine, so that the volume can be checked properly by first dismounting it.

Q. Isn't Windows XP running when CHKDSK is running?

A. No. CHKDSK runs at a preliminary boot stage before Windows XP is actually loaded into memory.

Q. My hard drive lets me run a File System Check in Windows XP, and I don't need to reboot. Why?

A. This is because you have no open files on the drive letter (C, D, E?) during the time you decided to scan for errors. Typically, this is a scenario where a drive letter does not have Windows XP installed / running on it.

Q. OK -- why does CHKDSK allow me to Attempt to scan and fix the Recovery of Bad Sectors while Windows XP is loaded?

A. Scanning for bad sectors is something completely different than scanning a drive for file system errors. Bad sectors are a physical defect in the hard drive, which may or may not be related to an open file, and which is also why Windows XP will allow you to perform such a task.

And since we're on the topic of Scandisk and Defrag for Win9x and how it constantly restarts:

I know that the best way to overcome this problem is to use a third-party application that doesn't hiccup like the Microsoft counterparts do. I also know that running Scandisk or Defrag even under Safe Mode won't always do the trick.

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