I don't know about Diamond (that's what you have, right?), but old Creative's driver (4.xx) does allow to turn on FSAA. It does not have "force FSAA" setting though.
I have it and I have it installed, but I have not noticed any difference even in performance so far.
Again, can anybody explain the whole issue with FSAA in TNT2? Why did it appeared and then disappeared from the drivers?
Regards,
Comer
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