Go ahead and overclock it. The TNT2 cards overclocks well!. Anyway you get more performance for free so why not try it?. I overclocked my TNT2 M64 & believe me it was great. I went from 1850 3Dmarks to 2650+ marks!. Not bad for a M64 ?. Definitely it is worth overclocking. I only used a generic 40mm fan over the heatsink which originally came with the card, & I think that is enough. Let me know your results after overclocking.
1. AMD AXP 2600+ @ 2.34Ghz (167x14) Cooled with CoolerMaster Aero7+ / Asus A7V8X-X (KT400) / 1GB 333MHz RAM / Maxtor 120Gb DMAX Plus 9 / GeCube Radeon 9600Pro / PixelView PlayTV Pro / Acer 21” Monitor / SB Live! / NEC ND-2500A 8x DVD±RW / Sony CRX-320EE Combo Drive
2. AMD AXP 1600+ (Stock cooler) / MSI K7T Turbo2 / 512Mb 133MHz RAM / Maxtor 80Gb DMAX Plus 9 / Gigabyte Radeon 9200 / Philips 17” Monitor / Sony CRX 160 CDRW / Asus E616 16x DVD
3. IBM 300PL PIII