Motherboard, RAM, CPU and power problems: POST beeps, no power, overheating shutdowns, blue screens, burning smell, swollen capacitors, date/time resets

Problems with the motherboard, RAM (random access memory), CPU (central processing unit) and power supply often produce dramatic symptoms: a PC that will not start, beeps instead of booting, shuts off without warning or crashes to a blue screen. Because these parts depend on each other, the same symptom can have several causes, so work from the simplest and most likely cause to the most complex, following the troubleshooting methodology. POST (power-on self-test) is the firmware's check of essential hardware each time the computer starts. If POST finds a problem before the display works, it reports it with beep codes, a pattern of beeps, or with diagnostic LEDs or a numeric code on the board. The meaning of beep patterns depends on the firmware manufacturer, so look them up in the motherboard documentation rather than memorizing them. In general, one short beep often means POST passed, and repeated or long beeps commonly indicate memory or video problems. A POST card plugged into an expansion slot can display codes on boards without built-in diagnostics.