DirectX 10 and DirectX 9 card

Will DirectX 10 improve performance on my 7900GTX?

I know its NOT a DX10 Card, but i would just like to know if it would run current and future games even better using DX10.

OK, but heres what i was thinking:

Surely DX 10 has more features than DirectX 9. But, it must have ALL of DX 9's features plus the extra new stuff.

So, one would assume that DX 10 should be be more optimized and efficient than its DX 9 counterpart. So, if my card can only use the features of DX 10 that DX 9 had, it should run games better, right?

Example: If DX 9 consisted of A B C D.
DX 10 should also have A B C D plus E F G H........
But DX 10's ABCD is more efficient/optimized than the DX9 version, my card will run better using DX10, right?

Haha, ok. Sorry.. My bad. Was just grasping at straws i guess.

So i cant even install DX10?

As it has been reported in the media....

DX10 is not compatible with previous versions. A very dramatic departure. DX9.0L is only for Vista so that current users with DX9.0 cards can use Vista. Microsoft is going to pull support from XP in the next few years as it has already done with 98 and earlier OS. There was a "road map" as to the timetable on one of the user sites a while back.

I can't see where an update to DX9.0c will be of any use to current XP users in this climate