WoW is both a opengl game and Direct3d game, if you want to try running opengl, do this, go to your WoW directory, create a shortcut of WoW.exe, place it on your desktop, go to properties on the shortcut, and in the target after World of Warcraft\WoW.exe" put -opengl so it would look like "C:\Program Files\World of Warcraft\WoW.exe" -opengl

thats all. Now the game runs a bit slower in opengl since opengl in WoW isn't done quite well, but give it a shot. I don't have a 3dfx card anymore so I can't test this unfortunately. My guess is the messed up texture problem will be fixed but the games performance may drop to unplayable, but thats my prediction, so I may be wrong.