Unfortunately, there is no tested list for Raid Controller Card. Actually, server products are NOT tested/validated on the Intel (R) Desktop Boards. To be honest, i heard that many server raid controllers dont work on the DG43NB.
This is nowhere to go into the bios to enable so that you can get the prompt to enter the RAID Bios for external raid controllers.
It does not work, then no chance to make it work.
All the best,
um, actually, I just ran into this same problem with the same board. I have an old Adaptec IDE raid controller, and it's bios wasn't showing at boot (just this screen for the motherboard). I found a setting under the security tab in the bios that fixed this (something about external card view or something). Now I see the bios just fine.
I hope this is able to help you.