Asus AP120-E1 - Manual (Page 20)

Chapter 2: Hardware setup 2-4
2.3 Motherboard information
The AP120-E1 comes with the ASUS P4P800S-E motherboard that uses
the ATX form factor measuring 12 inches x 9.6 inches (30.5 x 24.5 cm).
Make sure to unplug the power cord before installing or removing the
motherboard. Failure to do so may cause you physical injury and may
damage motherboard components.
The motherboard is secured to the chassis by ten screws as indicated by
circles in the illustration below.
Refer to the motherboard user guide for detailed information on the
motherboard.