1 short beep (Normal)
2 short beeps POST error
No beep: Power supply, system board, or system case built-in speaker.
Non-stop beep: Power supply or system board.
Non-stop short beeps: Power supply or system board (a key on the keyboard might also be stuck)
1 long beep and 1 short beep: System board
1 long beep and 2 short beeps: Video card
1 long beep and 3 short beeps: Memory
3 long beeps: Keyboard