I'd like to use boot from the onboard LAN of a P4SCE motherboard to install the OS, but when I choose "Legacy LAN" as the first boot option, it doesn't do anything. Does this board support LAN PXE boot?
Yes, it does. What you need to do is first set the "Onboard LAN Boot ROM" under "Advanced" --> "PCI/PnP Configuration" to "Both" or "LAN1" or "LAN2." Save and exit the BIOS. Then go back into BIOS and change "First Boot Device" under "Boot" from "Floppy" to "IBA GE slot 015." Save and exit BIOS again. After this, system should boot from LAN first.