Well the first thing that I can think of is using powerstrip to overclock it. After that to tweak it more you should go to the specific Nvivia oriented websites like Riva3d and see what they have to offer. The newsgroups in those websites are also invaluable sources of info.
I also would be careful which drivers you use. I distintly remember that some of the newer Nvidia driver sets actually decreased performance with the TNT-2.
beyond that I dont know what else you can do.