A boot sector is a sector of a hard disk, floppy disk, or similar data storage device that contains code for booting programs stored in other parts of the disk. A master boot record (MBR) is the first sector of a data storage device that has been partitioned. Since code in the boot sector is executed automatically, boot sectors have historically been a common attack vector for computer viruses. To combat this behavior, the BIOS often includes an option to prevent writing to the boot sectors of attached hard drives.
In case, the hard disk of your computer is infected with such a virus and you want to perform a boot sector fix on the hard disk, then you can try Avira Boot Sector Antivirus Tool. This freeware tool is provided by the noted security vendor Avira and is available for free download from their website.
The search and repair tool contains a signature-VDF as well as a user interface (ANTIVIR.EXE). If you want to search for boot sector viruses using the AVE32.EXE go to the commandline and enter: AVE32.EXE -allboot. If you want to use the user interface, then you can start ANTIVIR.EXE. Press ALT-F to open a window where you can choose which boot sectors to scan by entering T. Keep your boot sector clean and secured against malware with Avira Boot Sector Repair Tool!