From the doc: 'Fatal Error is a small but nasty little joke program. When run, it displays a message box that says 'Warning... Your system has become unstable!' and confronts the user with three choices: 'Abort,' 'Retry,' and 'Ignore.' Each of these three choices displays one of three equally frightening error messages... 'Erase All Data on C: ?' 'Format C: ?' or 'Delete OS?' Put this in the unsuspecting victim's Startup folder and watch them squirm!'
fatalerror.exe