Hey rix,
I don't posess any knowledge of that motherboard, but I can assure you that there are users who have installed Vista in a DFI board with no problems at all.
I find it awkward that motherboards don't work with Vista.. I mean, driver issue is one thing but hardware incompability is totally another..
Maybe you ran into some one-of-a-kind case.. Try getting support from DFI, in the meanwhile, I'll try to find anything that can help you.
On a second notice, that graphics card does look odd to run Vista, I had one myself.. Are you sure it's capable of rendering Vista's eyecandy? What about other hardware, what are you using?