so, the card will not perform up 2 the mark as in vista...XP doesnt support DX10, so simply DX10 = Vista.
difference between DX9 and DX10 is not monstrous or anything when speaking strictly about the graphics part.
In XP the card will run in DX9 mode and its ot bad at all seriously.
Yes for DX10, Vista is a must.
Try the third party developed DX10 For XP....! [JUST HIT THE GOOGLE]
If you u really don't have a high end Rig......simply don't try to Gaming on Vista.... It will suck you down.....