SFC /scannow is a super-useful command you can use in any Windows version. When the SFC (System File Checker) command is used with the /scannow switch, the tool will scan all of the important Windows files on your computer and replace them as necessary.
Missing and corrupt operating system files (like many DLL files) are arguably the biggest cause of major Windows issues. Considering that, plus the fact that SFC /scannnow is completely automatic and very easy to use, the tool should usually be one of your
first troubleshooting steps.
- 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
- 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.]
A message will appear stating that 'The system scan will begin'. Be patient because the scan may take some time
- If any files require a replace SFC will replace them. You may be asked to insert your Win7 DVD for this process to continue
- If everything is okay you should, after the scan, see the following message "Windows resource protection did not find any integrity violations"
- After the scan has completed, close the command prompt window, restart the computer and check.
Check the below mentioned link for further guidance on SFC scan –
http://support.microsoft.com/kb/929833
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