Computer tools and methods novelly combine periodic backup and restore features with migration features to transfer the components of a failed system to a new system. As well as backing up and transferring critical data files during the disaster recovery operation, an aspect of the present invention also transfers, inter alia, applications, user states, hardware settings, software settings, user preferences and other user settings, menus, and directories. In another aspect of the present invention, a network of shared end-user computers periodically backs up each individual end-user computer to a central instrumentality, in a novel manner to reduce storage and time requirements. That is, redundancies for the end-user computer backup files are eliminated or greatly reduced by only making reference to but not storing components that are generic to the system, and further for each previously stored component, only storing differential or incremental information, unless predefined conditions are met.