BOOT DISK:

A disk, which contains special, hidden, startup files and other programs to run a computer. A boot disk is usually specific to the operating system and version. There are several types of boot disks available to the average user ranging from a standard floppy boot disk to an emergency boot disk or bootable CD. It's important to use a boot disk when disinfecting a computer since most antivirus programs work best when they can gain complete access to the hard drive. In some cases failure to do so will prevent antivirus programs from detecting and removing certain viruses from the computer.