Overclocking your vid card too much won't damage anything else in your system. 99% of the time if you oc too far the comp will simply lock up and you'll have to turn the power off then power up again. I don't remember the default specs on that card... but I'd say that with proper cooling a 10% or more overclock could be achieved... with less than adequate cooling I wouldn't hope for more than a 5-6% oc. Good luck.
So far from 166mhz i brought it to 183, with an old cpu fan i dont use ~4000rpm i screwed it on the heatsink, and i just layed a heatsink and the other part of the CPU on the vid card, so it takes away a tab bit of heat,
I mannaged to get my Voodoo3 2000 up to 191Mhz. Stock was 143Mhz. Although past 179Mhz I got lower scores in 3Dmark2k1. I slapped a monster of a heatsink on it to do it though. Takes up the 2 PCI slots below the AGP. I don't expect to get any more out of the card though. I think the memory on the card is what's holding me back frm going any further.
I got 195 from the 3000 some time ago. I just took off the default HS, cleaned off the thermal pad they used...put some thermal paste on there reattached the HS. Then I screwed a 60mm fan on it, that I had lying around and that's it.
Use powerstrip to overclock the card