Blue Screen of Death; a Windows fatal system error, e.g. "A problem has been detected and Windows has been shut down" or "Your PC ran into a problem". Mention the specific error code and all information on the screen in your question.
"Blue Screen of Death" is the nickname of the "Stop Error", an error screen which appears when a Windows operating system (NT or later) suffers a fatal low-level crash, usually within a device driver.
The error screen consists of white diagnostic text on a blue background typically beginning with:
A problem has been detected and Windows has been shut down to prevent damage to your computer.
(Windows 7 and earlier)
Your PC ran into a problem and needs to restart.
(Windows 8 and later)
Be specific and include as much detail as you can about what you have changed just before the BSOD started happening as well as any error IDs or notices you see on screen at the BSOD dump.
If you didn't catch the BSOD display, information about the crash can be found in the System event log (viewable in the Event Viewer,
eventvwr.msc). Error events from the
BugCheck source contain the bugcheck code, the parameters, and the path to the dump file on the General tab. Critical events from the
Kernel-Power source contain the code and parameters in the
EventData section of the Details tab.
For a list of all possible BSOD errors and their descriptions, see the Bug Check Code Reference.