You are an IT technician for your company. Vivian has been receiving error messages indicating that some of her Windows system files are corrupt or missing. To fix this issue, you ran the Windows System File Checker tool (SFC.exe). Shortly after the files were repaired, Vivian calls again because she is still having the same issue. You now suspect that the corruption or renaming of the system files is being caused by malware. Which of the following is the next BEST step that should be taken?
A. Quarantine Vivian's computer.
B. Disable System Restore.
C. Perform a scan using anti-malware software.
D. Back up Vivian's critical files and perform a clean install of Windows.