Make sure you have the latest drivers from nVidia:
http://www.nvidia.com/content/drivers/drivers.asp
That said, I'm not sure the TNT1 is still supported... Check on the CD that was bundled with your card if you still have it.
Anyway, the idea is you must install a driver that support OpenGL 1.1 or better. Upgrading DirectX may help.
In the end, the easiest solution may be to just buy another video card, since even the lowest-end cards you could buy nowadays should run TF without any problem.