Open Run menu [ Win+R] and type Services.msc and hit the Enter key.
Look for Windows Modules Installer or TrustedInstaller.
If it’s present but disabled, set Startup type to Manual and start the service.
If it's missing then:
Open Command Prompt as Administrator and copy paste the following followed by pressing the Enter key:
sfc /scannow
You may download System Update Readiness Tool
If required, consider a Repair Install of Windows 7.