Why would you want to use dx7?
I think you are unlcear on how Dx works..even if your card is Dx9 compliant you can still run a dx 9 game(you must have dx9 installed of course), you just dont get all the new effects. You can code your effects so that there are fallbacks for non-shader cards etc.. even have no effects at all. Standrd A6 materials like mat_model, mat_shaded, etc will work on old cards.
