1. Click the 'Start' button and then click the 'All Programs' tab.
2. Click on 'Accessories' and then right-click on the 'Command Prompt' option.

3. Click 'Run as administrator' and then enter your administrator password into the field that appears on the screen.
4. Type 'sfc /scannow' into the command prompt and press the 'Enter' button.
5. Wait for the scan to complete and then restart your computer for the changes to take effect.