(Windows only) This option prevents a user from closing the window while a program is running by clicking on the "X" button or hitting ALT-F4. With or without this option, such an action will bring up a dialog box warning the user about the reasons not to abort that way and suggesting the proper way to exit. But without this option, the user can choose to ignore the warning and click on the "OK" button to proceed with the abort anyway. With this option, the "OK" button is deactivated. See XABORT option.