mine got messed up because I think I got a bit of AS5 around the NB and shorted something. the PCI bus and onboard audio failed, but EVERYTHING else worked fine (I even did a stability test with prime95 and it passed fine)
it had nothing to do with overclocking it.
anyways, what kind of heatsink do you have on it? if you have a good one, you should be able to push over 1.7v into it without damaging it (mine was set to 1.71v but would RISE to 1.77v under load)
here's the only picture I have of my highest stable overclock (I think I was able to get 2.6ghz stable but I don't remember, because I have clockgen overclocks of up to 2.68ghz)
I also had a VERY cheap motherboard. it was/is a Biostar NF325-A7 that came with a Venice 3000 for 60 bucks a few years ago on newegg.
to overclock, go into your bios, drop your ram timing a bit (if you have DDR400 drop it to DDR333) drop you HT multiplier from 4x to 3x, then raise your Vcore a bit, and start raising your FSB.