A user's computer fails to boot and displays an error message indicating a missing operating system. After troubleshooting, you suspect it might be a boot sector virus. Which action should you take to confirm and address this issue?
Use an antivirus rescue disk to scan and repair the master boot record (MBR).
Format the hard drive and reinstall the operating system.
Run a full antivirus scan from within the Windows environment.
Reinstall the operating system from a USB drive.