Basically, what WILL work on NT4, what MIGHT work on NT depending on user's hardware, and what WON'T work at all under NT.
From what I've pieced together, DX3 WILL work on NT, but no DX version after that, period. Somebody said that taking the Win2000 DX dlls and copying them to NT4 allows DX7. It would nice to know if this really works, but I'd like to talk about what comsumers currently have, which is NT4 plus whatever service pack. I've heard OpenGL might work, and I know OpenGL has always been a part of NT, but I think that's a different implementation than the OpenGL we all love.
So what's the real story (and please, if you're not sure about it, say "I believe ..." or something. I'm trying to weed out the false rumors). What APIs (video/input/sound/...) must a developer use to get a game running, or at least possibly running, on NT?