One of the most important features in current software applications is the undo command, which allows users to revert to previous states in their documents. A relatively unexplored concept involves system undo, a method of restoring settings in a system that were accidentally changed by the operator. This research paper discusses "a model of undo that matches the needs of human error recovery and retroactive repair." The authors begin by explaining the growing importance of such a mechanism and the issues that complicate its design. An example of a system undo model is given, and its basic implementation is described. Lastly, the report considers possible directions for future work.