i did something like that a while back, it was a coppermine celeron (man was that thing a brick) it was 366 stock and i almost hit 700mhz with the help of multipliers, overvoltage, and massively raising the fsb. was pretty stable, but was hitting load temps of 50C+ which is alot for an older celeron.
on the otherhand, i have another coppermine chip in my xbox pc (sig) thats 933mhz, and have almost his 1.5 on that thing, but it cant get past the xp logo, but with the help of a little freind called clockgen by cpuid, I hit 1.6ghz. thats one thing i love about the p3 class, they can take one heck of a beating!
all thats left for me is my dads emachines E366i2, dont know if its even capable of overclocking, but man, if it can, im gonna make sure and fry that sucka, i hate that pc, its nothing but bad luck, if it was up to me id drop that mutha f***** into a volcano! its loud, hot, freakin virus magnet, eats psu's for lunch, and has gone thru every harddrive ive put in it! (except for my 20gb seagate thats in it now)
btw, how are you overclocking it? thru the bios, or using a utility, or a little of both?