Asus P3-P5G31 - Manual (Page 44)

2-28 Chapter 2: Basic installation
2.12 Selecting the voltage
The system’s power supply unit has a 115 V/230 V voltage selector switch located
beside the power connector. Use this switch to select the appropriate system input
voltage according to the voltage supply in your area.
If the voltage supply in your area is 100-127 V, set the switch to 115 V.
If the voltage supply in your area is 200-240 V, set the switch to 230 V.
Setting the switch to 115 V in a 230 V environment will seriously damage the
system!