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How to Repair Corrupt or Damaged Windows System Files with System File Checker

Sometimes one of the important Windows system files can get corrupted. Then you may get messages about missing DLL files or have other indications that there is a problem. This tip will discuss repairing the system with System File Checker (SFC).

This is one of the numerous  command-line system tools that come on all current versions of Windows. It will scan all protected system files and replace incorrect or damaged versions with copies from a backup cache or from an installation disk or folder.

Malware infections are one source of this type of problem so make sure your system is clean before trying repairs. Also, System Restore is easier to use and should be tried first if possible.

Using System File Checker in Windows XP

1.    Open a command prompt (or the Start-Run line).
2.    Type and enter "sfc /scannow" (without quotes but with the space).

Your files will then be scanned and repaired if necessary. It may take 10 or 20 minutes, depending on your system.

Unfortunately, in Windows XP it is quite possible that SFC will first ask for your Windows installation disk. Most people only have a restore disk so it is necessary to take some rather involved steps before running SFC. Even if you have an installation disk, it probably won’t work unless Service Pack 3 is on it. A discussion of how to proceed if you have no proper installation disk is at this Bleeping Computer forum.  

Using System File Checker in Windows Vista/7 

The procedure generally goes much smoother in the newer versions of Windows. 

1.  Open a command prompt with administrator privileges.
2.  Type and enter "sfc /scannow" (without quotes but with the space). 

Your files will then be scanned and repaired if necessary. Again, it may take 10 or 20 minutes, depending on your system. 

If your Windows Vista/7 system won’t boot, there is still a possible way to try a repair. In such cases, SFC can be run offline using  the Windows Recovery Environment (RE). Again, the catch is that you need a setup disk. Details of using RE can be found at WinHelpOnline.

After running System File Checker

It is best to go to Windows Update after any repair is done to ensure that you have the latest file versions.

As an aside, my personal preference for dealing with corrupt files is regular backups. However, when helping other people (who didn't back up) SFC has its place and is part of the regular toolkit.   

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This tips section is maintained by Vic Laurie. Vic runs a Windows blog called The PC Informant and also operates a computer education website.

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by babagay on 14. December 2013 - 5:57  (112935)

has 25gb pysics,science,maths books.suddenly windows help system not working,networking not working,dsl stopped working.means windows got corrupted.restore points were deleted before this coz they werent working properly.sfc/scannow not working asking for windows xp sp 3 cd and when i put it in cd drive then a message comes to put cd in drive and this message comes repeatedly after some time.
if there is a virus its solution is antivirus.
if there is windows corrupted then whats solutiion.i mean there should be a more punishing name for windows xp corrupted.
there should be more than one soluition for windows corrupted not one or two solutions.

by MidnightCowboy on 14. December 2013 - 6:17  (112936)

We are unable to respond to support requests in the comments sections. Please post details of your issue here in our forum. MC - Site Manager.

by uros on 27. August 2013 - 12:44  (110348)

I have a problem whent a started an pc it shoved to press start windows normaly, safemode,safe mode with command prompt,last known good configuration and when i pressed evry one of them it showed up .Windows failed to start. A recent hardware or software change,might be the cause and this

Windows failed to load because a critical syset driver is missing or corupt and a bunch of other things and some status:oxcoooooof and after i press enter
choose an operating system to start.,or press
TAB to to select a tool then there is windows 7 to press and to press tab for windows memory Diagnostic and when i press enter again on wondows 7 it is back on the first page please help

by v.laurie on 27. August 2013 - 12:58  (110353)

Unfortunately, we cannot answer individual support questions like this in the comments. Please post your question in the forum: http://www.techsupportalert.com/freeware-forum/general-computer-support/

by LeocXD on 28. April 2013 - 16:57  (107368)

I have a problem where it will go to a certain percentage, then it'll say "Windows Resource Protection could not perform the requested operation". I've tried doing "sfc /scannow" over and over again but it won't work. What do I do?

by v.laurie on 28. April 2013 - 17:18  (107369)

Unfortunately, SFC fails for many reasons. This type of question is beyond what can be answered here. Please log in to the Freeware Forum and post your questions in General Computer Support. Please provide more information about your system when you post there. Knowledgeable people there will gladly try to help you.

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