I went to the Gateway website where after some time I managed to find a reference to the e3400, and even a BIOS update. I grabbed it, opened it and low and behold the readme lists a few supported boards.... Mine isnt there!
Supported models have BIOS IDs (the string at the upper parts not the AMI ID at the bottom) of 0AAVEP02 - 0AAVEP08. The version I downloaded was 0AAVEP09. The board I have says its a 0AAOUP02. I looked at pics on the gateway site of the supported boards, and they look the same. The specs listed are the same, but since the board doesnt have a removable flash chip Im not going to force anything. I tried running the flash prog as set up by gateway, and it didnt run (different IDs).
The full AMI string from the bottom of the screen is:
Edit: Problem solved.... A friend swapped his P3 mobo and case with this one since he didnt need support for an offboard controller of any sort.