Abstract: A virus-resistant disk has a "hidden partition" in which anti-virus software is stored; the hidden partition not only shields the software from many viruses, but provides storage space that does not reduce the disk's formatted or advertised capacity. The disk includes software to cause the computer to execute the anti-virus software. The invention provides a hidden partition by utilizing storage space on the disk that is not reflected in the size and geometry information stored on the disk, e.g., in the BIOS Parameter Block.