Asus P3-PE5 - Manual (Page 88)

5-28 Chapter 5: BIOS setup
Restore on AC Power Loss [Power Off]
Allows you to select to/not to restart the system after AC power loss.
Configuration options: [Power Off] [Power On] [Last State]
PWR Button < 4 secs [Instant-Off]
When sets to [Instant-Off], the system will go to Soft-off instantly when
power-button pressed for less than 4 seconds. When sets to [Suspend],
the system will go to Suspend when power button is pressed.
Configuration options: [Suspend] [Instant-Off]