Asus P1-AH2 - Manual (Page 30)

2-12 Chapter 2: Basic installation
2.9 Expansion slots
In the future, you may need to install expansion cards. The following
sub-sections describe the slots and the expansion cards that they support.
Make sure to unplug the power cord before adding or removing
expansion cards. Failure to do so may cause you physical injury and
damage motherboard components.
2.9.1 PCI slots
This system has two PCI slot that supports cards such as a LAN card, SCSI
card, USB card, and other cards that comply with PCI specifications.
2.9.2 Installing an expansion card
1. Lift the PCI riser card assembly.