No such thing as a dual or quad core Pentium 4. There was a Pentium D that was dual core. The first quads were Core2 Q6600/6700.
I just threw away a Pentium 4 530 and motherboard that was just taking up space in the basement. I can't imagine why you want one. They are not even powerful enough to watch HD video. Check local computer shops. They may have one laying around they will just give you.