I can't use Dx7a because I get very strange visual effects with it. My monitor changes from normal to a sort of wide-screen, plus everything looks a little smashed. I tried it once, ran into those troubles and said forget it. I'd rather use Dx6.1 and have some strange in-game effects [EG fading sound] than use Dx7a and have everything look strange.
Since my vid-card is an old Creative Labs Banshee, there aren't any drivers that will let me use Dx7a with it. I did it the first time by dloading the 3DFX Voodoo Dx7a patch and running that. The patch caused the odd visuals, and Dx7a just screwed up everything else.
Once money becomes a larger factor I intend to simply buy a new computer. That'll solve my crummy FPS problems, Dx7a trouble, maybe even the fading sound bit.
NOTE: I e-mailed Pyro just before 1.03 came out asking about Dx6.1 and whether or not it'd work. He told me he uses it, and that there should be no problem using Dx6.1 for a while yet.
Flakbait