On a card that old, you may want to replace the fan with a new one. Fans on older cards usually stop working, and then the card fries. Compusa sells a chipset fan with heatsink and paste for $10.
Since that card is a TNT2, I imaging the default Nvidia drivers will work with it. To OC it, you use the "Coolbits" hack to unlock the overclock utility. To do this, you edit the registry, or you download a .REG file and run it, which adds the key to the registry for you. Search Yahoo or Google for the word "Coolbits" and you'll find it. Once you have the hack done, you click on Display, Settings, Advanced, the NVidia tab. and a menu should appear to the side of the window. One of the choices is Overclocking Frequencies.