A. More and more DVD hardware now works under Windows NT including the Creative Labs Encore bundle which I recently installed in my NT machine but it crashed every time I tried to watch a DVD. After much digging the problem was because DMA was enabled and after disabling DMA it worked fine and I can now happily watch the Matrix while I'm supposed to be working :-) This is not to say you should all disable DMA as its a good thing but if the hardware does not correctly support it problems can occur.
For information on setting DMA options see How do I enable bus mastering (DMA) in Windows 2000? and How do I enable Bus Mastering in Windows NT?