Hi,
From the Start Menu, open All Programs, open Accessories, right click the Command Prompt and select 'Run as Administrator'. In to the prompt type the following command and hit enter. Note: If you're running Windows 8, see the guide Hereon how to open an elevated command prompt.
sfc /scannow ( note that there is a space between sfc and the / )
Let the process complete, then type exit and hit enter.
Restart the notebook and when windows has reloaded, run the command again.
When completed, then type exit and hit enter.
Next, click the Start Menu, click Computer ( for Windows 8.1, click File Exploter, This PC ), left click Local Disk C once to highlight it, right click Local Disk C and select Properties. Click the Tools tab and then click the button to 'Check the Drive for Errors'. In the following window make sure both boxes are ticked and then click Start. Agree to schedule the check at the next system restart and then restart the notebook - this process can take several hours to complete before loading back into Windows.
Regards,
DP-K