Any idea if NT 4.0 will run on a new Asus 800 MHz FSB dual Xeon Nocona board with 2 Nocona 3.0 GHz CPUs?

Nope, I have no idea without really trying it out. My thinking is that NT4 will not properly support the extra features and functionality of both the motherboard chipset and the cpu.

I however would not see any reason why it wouldn't at least attempt to install, but I could see that NT4 would not see 4 cpu's, i.e., two physical and two virtual cpu's but only see the two physical cpu's

Yeah, Same here, I don't run on windows NT so i woudln't know if it would support an Asus 800 fsb mobo.. because i dont know compatability with that op sys sorry bud.
If i were you id switch to xp pro but you've probably got a reason for using nt

Yes, I have a professional video capture board and video edit software that is only compatible with NT. The PCI controler on the previous MoBo failed. So I have to find a way to repair it. I want to go to XP, but we can't spend the extra $10,000 it will cost for a new video board and edit software just yet.

So what is the make/model of the old motherboard ?!?

Have you tried locating a used/refurb motherboard to replace the one that just died ?!?

It's also possible that you maybe able to find a suitable sub, in that it may not have to be the same make/model, but rather one that has the same chipset and supports your CPU and memory, etc....

NT4 might work on it.

NT4 works on my ASUS A78NX and even has drivers for it. If the board as NT4 drivers then it should work fine.