Because you are using Windows 7, you could try a system restore or you could also boot to the Windows Recovery Environment (RE) and attempt to run sfc /scannow from command prompt there. The next step would be contingent upon which version of Windows you are using. Can you update now? For more information on this service failing, you might find this Microsoft Knowledge Base article helpful. The first question that comes to mind is have you gone into your services management utility (services.msc) and ensured that Windows Modules Installer is enabled? If you attempt to enable it and it fails, you might want to try to change the setting, for example, from manual to disabled and restart your system.
