I need more information on this elusive "Legacy OPROM"

In a past posting, Xelelion mentioned something about a "legacy OPROM" on the Predator AG3620 system but he did NOT mention whether it was a jumperpin he tripped across or something in (what they used to call) the BIOS>
Sadly this forum does not allow me to ask him directly via PM as it apparently is for 'the elite'

Calling the support line just gave me telephone solicitor in India by name of Ganesh that either refused to answer OR HAD NO TRAINING IN HARDWARE SUPPORT and thusly COULDN'T ANSWER!

THIS IS THE THREAD I REFER TO:
http://community.acer.com/t5/Gaming-Hardware/Predator-G3620-Booting-to-USB-CD/m-p/60241#M276