Disk Diag takes its name from utility tools that used to exist on old Atari computer devices, and it does roughly the same thing in that it cleans up application caches, empties temporary downloads, and removes things from your trash bin. It is a very basic program for removing temporary files, and may be useful to use prior to running a full system checkup with your paid antivirus software. Turn off your device, and it does most of what this app does because it mostly removes temporary files; except for clearing your recycling bin, which you would normally have to do manually.