Asus Z87 pro help

i got a asus z87 pro with a 4670k. got a mild overclock on it of 3.8 ghz from asus ai suite 3 software, but it is preventing it from going into c state. how do i remove that overclock.

easiest thing is probably clear your uefi.. you can use direct key or reboot into bios function from within windows then reset to defaults.