That's the PXE boot client. It's used to boot up in this "terminal mode" without any OS installed when it sees a server running PXE. RIS uses it to install OS images.
Haven't read or heard about it much since the Windows 2000 days. I think it's pretty much dead technology. I've only used it for RIS images, but that sucked too.
You can turn it off in the BIOS. It will only slow down your POST.