Abstract: Disclosed are a system and method for loading diagnostic routines images from disk for execution in a computer system. The method comprises the steps of (1) executing a boot loading routine stored in non-volatile memory within the computer system, the boot loading routine providing an environment in lieu of an operating system of the computer system within which to execute diagnostic routines, the boot loading routine including a disk access routine, (2) retrieving a diagnostic routine stored as an image on a disk into video random access memory ("RAM") with the disk access routine and (3) executing the retrieved diagnostic routine under control of the boot loading routine. The present invention, in its preferred embodiment, allows relatively large diagnostic routines to be stored in the form of images on a disk drive in the computer system and retrieved, as required, into video RAM for execution, without requiring the computer's operating system to function.