Mod Edit: Split from http://www.bleepingcomputer.com/forums/t/437688/intel-undi-pxe-20-screen-at-boot-up/ - Hamluis.
I was trying to install Windows 7 Starter from a bootable USB and I got this same error. Upon reading this threat, I found the solution. In the boot-up list in your BIOS menu, you have to remove the Atheros boot agent / LAN from the list.
It will then boot to whichever boot-ready device you've got.
I know this doesn't solve the entire issue of this threat, but at least it'll remove this pesky error.
Edited by hamluis, 12 February 2015 - 12:20 PM.