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What is the System File Checker, and how do I run it?

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Summary: The System File Checker is a little known utility that validates that Windows own files are undamaged. It's simple to run command line program.

What is the System File Checker, and how do I run it?

Windows XP works very hard to maintain the integrity of the system files on your machine. If you try to replace one of the "protected" files you may get an informative message that the operating system has put the old approved version back. Not all files are under system file protection and even for those that are there are ways around it. Occasionally system files become corrupt.

Enter the SFC, the System File Checker.

SFC is a good utility to run when you suspect that system files have been somehow corrupted. It validates the digital signatures of all of the Windows system files and restores any that it finds are incorrect. It will use the on-disk cache if possible, but SFC may require that you provide your original installation CD or a location with an image thereof. (See this prior article about not having an installation CD on some of the alternatives if that's the case.)

To run the system file checker press Start, Run, and then type in SFC followed by its options.

The most common usage of SFC is this:

SFC /scannow

This causes SFC to scan your system immediately. SFC can take a few minutes to run. As I said above have your installation CD or equivalent available in case SFC needs to replace a damaged file.

While it's not documented anywhere, if SFC replaces any system files I'd reboot. I just like to make absolutely certain that the file replacement actually takes effect.

The Microsoft knowledgebase includes more detailed SFC documentation including more options to check at boot time, control the size of the system file protection cache, and so on. Speaking of which, the knowledgebase also includes System File Protection documentation covering the mechanism Windows XP uses to keep your system files safe automatically.

UPDATE: If you have no CD, but you do have an I386 directory or CD image somewhere, check out this article: How do I tell Windows where my I386 folder has moved? Once you make the changes therein, you should be able to run SFC to completion.

Related:

Article 154 | Posted February 28, 2004

Recent Comments
190 Comments

Hey leo I had to get rid of antivirus xp2008 and i dunno if i corrputed some things in the process
Now add or remove programmes will not work:(
Nothing happens at all when i click it
I tried sfc but when i pressed enter it flashed up for a brief moment and then dissapeared
Any help:s

Posted by: CAL at August 26, 2008 9:47 AM

Leo,
All of a sudden an XP PRO computer boots, but
stops with the error message that the windows\system32\config\system file is either missing or corrupted. The file exists and is about 5 meg, so it must be corrupted.
I read your article about using sfc /scannow,
however when I use the original OS CD to boot and get to a command prompt with the "r" recovery option, the sfc.exe is not an available file to run.
Is it on the OS CD?
If not then trying to fix a damaged system file
that is keeping the OS from loading using the sfc
command is useless. No START RUN available !!
What am I missing? If it can't be run from the Recovery Console, then you should tell your readers that for 95% of the time they can not fix a computer that is stuck because of a corrupted file.
Greg Fiore

Posted by: Greg Fiore at September 10, 2008 7:12 PM

Thank you for this info! I found it most helpful. I ran a SFC with my start up disk and now my computer is running better. Thank you! I find your tips as always, useful!

Posted by: Buckshot at September 19, 2008 2:01 PM

Is there a potential problem when using SFC and you have updated your system with various service packs. It seems like some of those critical system files would have changed, and there you are putting in your ORIGINAL install disk with "old" system files on it.

Posted by: Ray Brumbaugh at September 23, 2008 11:54 AM

I can't run SFC from the start/run or even if I us the start/run/cmd, with the start/SFC it will flash for just a splic second and the go away, I even tried to run it in safe mode with no luck,
but with the start/CMD/SFC I get this
"Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.

C:\Documents and Settings\Keith>sfc
'sfc' is not recognized as an internal or external command,
operable program or batch file.

C:\Documents and Settings\Keith>
I ran chkdsk and that works fine, any help would be nice.

Posted by: Keith Morton at October 3, 2008 2:53 PM

When running system file checker use:sfc /scannow.
Be sure you leave a space between the c and slash.
As sfc /scannow.

Posted by: Duane Foster at October 18, 2008 11:08 AM

I just successfully ran System File Checker on my custom built PC using my Windows XP Home Edition master disk. Interestingly, the disk would not run in my CD drive, but ran perfectly in my combination Benq DVD writing drive. After the System File Checker ran, I saw no error messages. I have been trying to solve a problem, trying to determine why my front USB ports have stopped recognizing my Digital Concepts card reader/writer.

Posted by: Mike Creel at October 28, 2008 3:38 PM

2 problems;

First, I STILL get the red x's and send/receive grey boxes for pics.
Second, I have HPPhotomsmartessentials STUCK, after deleting the program from all files I know of.

Posted by: Bruce Boepple at November 18, 2008 4:28 AM

need help lost my start up progams and can only
start up in safe mode

Posted by: william at November 26, 2008 3:10 PM

hey Leo,your article is interesting and straightforward for beginners to assimilate.that's very thoughtful of you and i really appreciate it.Can u please publish an article on "how to do some minor things on the computer system" so it'll be an added advantage .i'll be glad if u can do that.

Posted by: IDAYAT at November 27, 2008 4:29 AM

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