I don't know if I'm right, but I've heard somwhere that DX10 is going to be a new one that isn't backward compatable... I think that you'll have to buy a new graphics card to run it and the games that use it...
But i have heard that it is compatable backward and DX 9 games are safe for few more years.And i don't think windows xp is compatable with DX 10.and it can't be just upgraded
It's not true DX10, since theres no DX10 hardware compatible video cards released yet, and DX10 isn't even done the development stage yet.
To answer your original question, no, DX10 isnt compatible with XP Pro, since it uses a completly different API (I believe), which only Vista offers. But you can use DX9 games and hardware on Vista.
That doesn't mean it's not true DX10. If you have Vista, do a dxdiag on it and see what it tells you.
Even though there are no cards for it yet doesn't mean anything. We are talking about backwards compatibility. It will be, but some games it has problems with. I don't know if that will be fixed by the time they're done or not.
Well i have just installed vista and found it very impressive.But the drawback is i can't play games.It gives error message and also can't surf to internet,which makes me roll back to winXP again.