I built my 680i/X6800 back in 12/06. There were many problems then since it was cutting edge at the time.
If you still can't resolve problems, start from square one.
Use only 2 sticks of ram. XP won't see more than 3.63 and XP has had some problems with that. Look at the manual and place them exactly as shown for 2gig.
Pull all you nics and XFI and only have your vid installed.
Reformatt HD and use mobo setup cd with those drivers.
Install XP1. Is it a slipstreamed copy or original?
That should get you up and able to get ethernet authorized.
Go to EVGA.COM and load current mobo drivers if any.
Then intall vid drivers, install XFI, then nics.
You'll probably have to have Billy re-authenticate your OS if its original. Not sure about slipstream.
Backup your registry so you can reload if anything goes haywire.
Then reinsall ram to 4 gig.