I replaced my stock P4 heatsink with the Zalman7000 aluminum/copper heatsink.
http://www.newegg.com/app/ViewProduc...118-108&depa=0
It's MUCH quieter than the regular heatsink and cools very effectively. When I'm just web surfing or idling my cpu temp is around 27 C, during gaming the highest it goes is probably 43 C. Also, I chose the hybrid alumin/copper instead of the pure copper because the pure copper version is insanely heavy.