PCI latency (bios) ?

I have a P4B that will overclock the fsb to 120 /125, then winXP gets screwed up. I'm pretty sure it's because the H/D is runnining way out of spec. Anyway I don't see a pci lock option in my bios. Just wondering if the PCI latency timer "Leave this field to the default setting [32] for best performance and stability" is in fact my pci lock. If it is, should I decrease this value [32] by a 1/3 ratio to match the increase in fsb overclock. Of course I am going to try it, just wondering if anybody could offer any insight.