Go to Start, type cmd and open the utility using Administrator rights. Type net localgroup "Administrators" "NT Authority\Local Service" /add press the Enter key and reboot your PC. If you still cannot use the application, go again to Start, type Turn Windows features On or Off and open the tool. Press the + sign next to Media Features and un-check the Windows Media Player box. After you restart the computer go again to Windows Features and check the Windows Media Player option. Another solution can be the utility provided by Microsoft. Click the Run Now button, save the file to your computer and follow the instructions.