Several months ago on an HP DC7800P small form-factor PC, I installed Ubuntu Server and have been using it as a fileserver (plugged into a UPS). Today I moved it and was reminded that it had no capability to retain BIOS settings, so I went in and set time/date. But the Ethernet isn't working. Ubuntu says it's not there, and more ominously the light on the Ethernet switch for that computer's Ethernet cable does not light up. I'm guessing it has something to do with BIOS settings. I've played with two so far, to no avail:
Security->Network Service Boot->Disable
Advanced->Device Options->NIC PXE Option ROM Download->Disable
Security->Network Service Boot->Disable
Advanced->Device Options->NIC PXE Option ROM Download->Disable