Being as DX9 and DX10 won't be compatable, they will have to release 2 versions of every game for a while (would probably include them both in the same package), or just have to deal with games running like crap on Vista in their emulated state, which I don't think they will want.
UT2007 will be so demanding systems will have a hard time handling it at full settings under XP, they can't afford the performance loss of emulating that game or games on its engine.
UT2007 will be so demanding systems will have a hard time handling it at full settings under XP, they can't afford the performance loss of emulating that game or games on its engine.