How To Use SFC /Scannow to Repair Protected Windows Operating System Files

The sfc scannow option is one of several specific switches available in the sfc command, the Command Prompt command used to run System File Checker. Sfc /scannow is the most common way that the sfc command is used.
Sfc /scannow will inspect all of the important Windows files on your computer, including Windows DLL files. If System File Checker finds an issue with any of these protected files, it will replace it.
Important: You must be logged in as a user with administrator rights in order to run the sfc /scannow command.
Follow these steps for using sfc with the scannow option to repair important Windows files:

Difficulty: Easy

Time Required: Using sfc /scannow to repair important Windows files usually takes 5 to 10 minutes.

Here's How:

1. Open Command Prompt.
   Important: You must run Command Prompt as an administrator in Windows 7 and Windows Vista to use System File Checker.
   
2. Once Command Prompt is open, type the following command and then press Enter.
   

   sfc /scannow
   

   Note: There's a space between sfc and /scannow.
   
3. System File Checker will now verify the integrity of every protected operating system file on your computer.
   Note: In some situations, especially in Windows XP and Windows 2000, you may also need access to your original Windows installation CD or DVD.
   
4. Restart your computer if sfc /scannow did actually repair any files.
   Note: System File Checker may or may not prompt you to restart but even if it doesn't, you should restart anyway.
   
5. Repeat whatever process caused your original problem to see if sfc /scannow corrected the issue.