My overclock kill my sata... help

I just bought a p4 3.0e combo at frys with an ecs 848p mobo. Every thing runs fine on it until I put in my sata hard drive. Itwont let me overclock at all with the sata conected. W/O it conected (my pata hd) I can get it to 240 fsb with no vcore adjustment. Which bus is the SATA conected to? I thought it was running on the pci bus and since I have the pci bus locked I should not have this problem. BTW I think the sata controller is ICH5 but Im new to intel so Im not sure of that.