1. Insert the Windows installation disc into your computer's CD/DVD drive.
2. Close the installation window if it appears.

3. Click the 'Start' menu button located in the lower-left corner of the Windows desktop.
4. Locate the search box located in the lower-left portion of the start menu.
5. Enter the text 'run' (without quotations) and press the enter key. This will cause the 'Run' dialog box to appear.
6. Enter the text 'sfc /scannow' into the run dialog box's text box and press the 'Enter' key. This will start a scan of all the Windows system files. Any system files which are damaged or have been changed erroneously will be replace with the version that shipped with your Windows installation disc.