Is this the file you tried?
http://members.driverguide.com/drive...riverid=431020 (2525)
From what I've read googling, this appears to be an Intel built motherboard however, Intel is of no help either. You might dig around on the Gateway Japan website to see if you can find any info.
http://www.google.com/url?sa=U&start...3D707JP&e=9797
Another thought, the file you downloaded could have been corrupt causing your problem. If you want to download it again and try over here's the link to the current bios file:
http://support.gateway.com/support/d...628&dscr=South Lake, South Lake 2, South Lake 3, and Luxemburg Motherboard BIOS Update Revision: SE91510J.15A.2609
and here's a post I found dealing with specific instructions for installing the bios file...
http://service.gateway.com/s/issues/2-1890594513.shtml
And last but not least, did you disable the onboard video in bios setup?