That's due to the encoding into Vista there. One thing seen at Microsoft regarding DX 9 and previous versions is the continued updates which will most like see the equivalent to DX 10 while still requiring the original DX 9c be installed first and then updated when installing XP, 2K, ME, 98. Some form of updated drivers would have to be downloaded in order to see newer DX 10 orientated games run on an XP system. Presently both the early DX 10 included and DX 9c are on the Vista installation here.