MSI MS-6551 User Manual page 31

Hardware Setup
Speaker
Speaker from the system case is connected to this pin.
If on-board Buzzer is available:
HDD LED
HDD LED shows the activity of a hard disk drive. Avoid turning the power
off while the HDD led is lit. You can connect the HDD LED from the system
case to this pin.
Power Switch
Connect to a 2-pin push button switch.
2-19