[s]Sounds like an infected pc with more problems than BG can cope with initially.
Do you still have an internet connection? If so I'd get Malwarebytes downloaded and installed first,
https://www.malwarebytes.org/
Make sure once it has been installed that you can UPDATE it. If so run a 'Quick Scan'.
After that try BG again. If you're still getting the same error you have damaged OS files.
https://support.microsoft.com/kb/812340[/s]