If you have a corrupted file in Windows 7 or Vista, click Start, type “cmd” into the Search box, right-click on the Command Prompt and then select Run as Administrator. Provide the administrator password if prompted, or click Allow when a confirmation window appears.
In Windows 8 or 8.1, hover the mouse over the lower-right corner of the screen, and click Search. Type “command prompt” into the Search box, right-click on the Command Prompt, and then click Run as Administrator. In the black Command Prompt window, type “sfc/scannow” and Press Enter. Windows scans the corrupt system files and repairs them automatically.
To find and fix corrupt files in the hard drive of a computer running on Windows 7, click Start, and click Computer. Right-click on the specific hard drive, select Properties, and open the Tools tab. Click Check Under Error-checking, provide the administrator password if prompted, select Automatically Fix File System Errors, and then click Start.
Alternatively, if you have recently installed particular software or updates into your computer that cause unwanted changes, open the System Restore tool on your computer, select an earlier date to restore the computer, and then click Next to begin the restoration process. This option restores the computer to an earlier date when it was working properly and does not delete existing files or programs.