We've already been over this a few times...
Think of it this way: having a heat spreader is functionally the same as cutting a 3/32" layer of metal off the bottom of your heatsink and attaching it to the CPU core with thermal epoxy. When the larger part of this hacked-up heatsink gets put back on, you end up with an imperfect fit where the heatsink got cut in two. This doesn't improve heat dissipation; it hinders it.
If the heat spreader is of a more conductive material than the heatsink itself (i.e. as in the Silverado, where the main heatsink block is aluminum, but the contact surface is a slab of pure silver), then it might help. But this usually isn't the case, especially with the P4's stainless-steel heat spreader.
A heat spreader aids in heat dissipation only if there's no better passive cooling on the core.
<pre>We now <b>return</b>(<font color=blue>-1</font color=blue>) to an irregular program scheduler.</pre><p>