Longhorn needs DX 9 card
 

LONGHORN IS A DIRECT X10/NEXT operating system, but I guess you knew this all along. No one knows whether we are talking about DirectX 10 or NEXT in its name but we know it will come with Longhorn. Can we sneaky peaky tell you that it will use Shader Model 4.0, oops, it's too early to talk about that it's still tabu.
Does Microsoft know? We doubt it.

ATI said that for many aspects of Longhorn you will need DirectX 9 compliant graphic. I don’t know which card our friend Dave has in mind. I think by early 2006 you won't be able to play anything if you don’t have at least Direct X 9 card. For full expririence you will need DirectX 9 card. 3D Windows perhaps with Shader 3.0 if you ask Nvidia or 2.0 if you ask ATI.

http://www.theinquirer.net/?article=17854