Even if you get it to OC, it will never get close to a dual core. You might get it up to 3.2 or 3.3 GHz if you're lucky. The P4s weren't the best overclockers and when you OC them, they generate a lot of heat (which they do not OCed, but worse). If you need something faster, it's time to get a new mobo and CPU (and maybe other components depending on what you have).
Not what you wanted to hear I'm sure...