http://bugs.winehq.org/show_bug.cgi?id=14939
--- Comment #2 from Ben Klein shacklein@gmail.com 2008-08-21 18:09:44 --- (In reply to comment #1)
DXTC requires the opengl s3tc extension. On open source drivers you need to install a custom library for mesa to get it as the compression isn't shipped by default since it is patented. For that reason we can't also add it to Wine.
I see. And presumably, native dlls wouldn't help here either.