Abstract: The invention is an interlocking lockout device for a computer system. The lockout device comprises a locking disk dimensioned similarly to a floppy disk for so that it can be inserted and locked into a disk-drive. An engagement member of the locking disk interlocks with a bezel. In a locked position, the bezel covers the disk-drive preventing the locking disk from being removed from the disk-drive and preventing foreign matter from being inserted into the computer and disk-drive. While inserted, the locking disk keeps the computer system from booting and thereby prevents unauthorized operation of the computer system. The bezel and locking disk are adaptable on any size disk-drive and can easily be installed on different systems. This provides a lockout capability for computer systems with multiple drives and variable sized disks.