Open CMD.exe as admin,
- Use Windows + "X key"
- Choose "Windows Powershell (Admin)"
- Type in: SFC /SCANNOW
- Let this run and fix any file problems
- Now run: DISM /Online /Cleanup-Image /RestoreHealth
- This may stall from time to time as it fixes registry entries.
Once these are both done restart your PC and scan for viruses using your preferred antivirus.