How to run SFC ( System File Checker )

1. Open Command Prompt as an administrator, often referred to as an "elevated" Command Prompt.
   Important: For the sfc /scannow command to work properly, it must be executed from an elevated Command Prompt window in Windows 8, Windows 7and Windows Vista. This is not required in previous versions of Windows.
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.
   Important: If you're trying to use System File Checker from the Command Prompt available from Advanced Startup Options or System Recovery Options, see Tip #1 at the bottom of the page for some changes in how you execute sfc /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