When experimenting with overclocking I found that on my motherboard (ABIT IC-7) with a P4 2.8C CPU, any clock speeds over 220 causes my HD (10k RPM 36GB Raptor) to fail detection on the SATA bus.
Also, if the SATA ports are native on your chipset, they're from the southbridge, which is unaffected by PCI lock. If that's the case, you could get a SATA card