Slang phrase referring to the error message when Microsoft Windows experiences a fatal error condition. The monitor screen turns blue and fills with a typically cryptic description of the reason that your computer is going to crash and any data not saved to the hard drive will be forever lost. If you are very lucky, you can reboot your computer and restore the system. If you are not very lucky, you had better hope that you had the good sense to back up your system recently. Earlier MS-DOS systems lacked color and suffered the Black Screen of Death.