unfortunetly being a celeron you won't see much of a performance increase if any, the reason being that you can't increase the L2 cache and thats the biggy w/performance.
you're saying you went from 8x100=800MHz to 12x133=1.6GHz
basically doubling the speed. I would need screenshots, because you can't just raise your multi like that and the FSB so easily and not have anything happen to your computer. Raising the multiplier is dangerous, you're adding another 100 or 133 depending on what your FSB is. You are supposed to start with the FSB and raise it there. I simply don't believe you changed it from 8x100 to 12x133 with absolutely no problems whatsoever.
because you said your default multiplier was set at 8 and your default fsb was set to 100, 8x100 = 800MHz, if you have 12x133 = 1.6GHz that's still under 1.7GHz so you need to probably have default multiplier of 13 or 12.5 You cant take a screenshot of your BIOS you get a program like CPU-Z and it'll show your FSB and multi.