OK, well, from what i can tell, you;re being a bit too agressive in your approach.
Firstly, you bough a 2400+, and as far as overclocking potential goes, I don't know what you can expect, seeing as the Thoroughbred B line will cop out at 2200MHZ, on average. So seeing as though your comp is not booting up even with w 5:4 ratio (which takes the memory out of the equation), then your CPU probably can't handle runing at 2166 MHz. Simple as that.
So what you have to do it A:) overclock at small increments to find your CPU's threshhold. or B:) get a better cooling solution.
However, seeing what marginal results you will be capable of getting, i.e 166MHZ, it's hardly worth the investment. I personally say you save your time and don't bother overclocking. As the gains will be minimal.
Also having PC2100 is a major issue here. Depending on what make it is, and what latencies it's runing at at default speeds, you can judge it's overclocking potential. [I.E. if it's low latency runing at 133MHz, it may have potential to go higher. You can try increasing the latencies to overclock it if it's unstable at higher speeds, which really defeats the purpose of overclocking in the first place, especially if you can only boost it marginally].
As far as locking the PCI and AGP clocks, that depends on the motherboard chipset. Some have locked frequencies, but only for some chipsets, which I can't name since I don't know. Read your motherboard manual to find out, or look up info on your chipset to see what's the case (or look in the BIOS)
Anyways, from your current setup it looks like you will be able to get a marginal overclock.
