System File Checker tool

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How to use the System File Checker tool (SFC.exe) to troubleshoot missing or corrupted system files on Windows Vista or on Windows 7.

If a Windows Resource Protection (WRP) file is missing or is corrupted, Windows may not behave as expected. For example, some Windows functions may not work, or Windows may crash. The System File Checker tool (SFC.exe) scans for missing or corrupted system files and repairs them. 
Use the System File Checker tool (SFC.exe) to determine which file is causing the issue, and then replace the file. To do this, follow these steps:

1. Open an elevated command prompt. To do this, click Start, click All Programs, click Accessories, right-click Command Prompt, and then click Run as administrator. If you are prompted for an administrator password or for a confirmation, type the password, or click Allow.
2. Type the following command, and then press ENTER:
   sfc /scannow
   The sfc /scannow command scans all protected system files and replaces incorrect versions with correct Microsoft versions.

To determine which files could not be repaired by the System File Checker tool, follow these steps:

1. Open an elevated command prompt.
2. Type the following command, and then press ENTER:
   findstr /C:"[SR] Cannot repair member file" %windir%\logs\cbs\cbs.log >sfcdetails.txt
   Note The Sfcdetails.txt file contains details from every time that the System File Checker tool has been run on the computer. The file includes information about files that were not repaired by the System File Checker tool. Verify the date and time entries to determine the problem files that were found the last time that you ran the System File Checker tool.
3. Type the following command, and then press ENTER:
   edit sfcdetails.txt
   The Sfcdetails.txt file uses the following format:
   Date/Time SFC detail

The following sample log file contains an entry for a file that could not be repaired:

2007-01-12 12:10:42, Info                  CSI    00000008 [SR] Cannot 
repair member file [l:34{17}]"Accessibility.dll" of Accessibility, Version = 
6.0.6000.16386, pA = PROCESSOR_ARCHITECTURE_MSIL (8), Culture neutral, 
VersionScope neutral, PublicKeyToken = {l:8 b:b03f5f7f11d50a3a}, Type 
neutral, TypeName neutral, PublicKey neutral in the store, file is missing

If the System File Checker tool cannot repair a file, follow these steps:

1. At an elevated command prompt, type the following command, and then press ENTER:
   takeown /f Path_And_File_Name
   For example, type takeown /f E:\windows\system32\jscript.dll.
2. Type the following command, and then press ENTER to grant administrators full access to the file:
   icacls Path_And_File_Name /GRANT ADMINISTRATORS:F
   For example, type icacls E:\windows\system32\jscript.dll /grant administrators:F.
3. Type the following command to replace the file with a known good copy of the file:
   Copy Path_And_File_Name_Of_Source_File Path_And_File_Name_Of_Destination
   For example, type copy E:\temp\jscript.dll E:\windows\system32\jscript.dll.