Well, the Pentium IV can always use the extra bandwidth, the question is whether your motherboard can handle memory speeds of 200 Mhz (x2). You would have to run your machine at out-of-spec FSB speeds to even achieve such memory speeds, since currently no P4 chipsets support DDR 400 officially (as far as I am aware). If you have a highly tweakable motherboard, it might be possible.
And if you want the most knowledgeable people to help you out with your question, you should probably make your thread title a lot more informative, otherwise most folks will just skip over it.