A Computer crash is when a computer program stops running normally. The program can be either an application or the computer's operating system. The program may freeze (stop) or may show a crash report explaining what happened. One, called the Blue Screen of Death has a blue screen and means whatever you were working on may have just 'died'. Many crashes involving computers are often the result of machine instructions not running right. Typical causes are if programs' counters are set to incorrect addresses or buffer overflows.