Okay strike that last barebones that I posted. While it's infinitely superior to what you're running now, and would be compatible with all your present gear, I neglected the fact that you listed an AGP video card, so here we go.
http://www.newegg.com/Product/Product.a ... 835106606RThis is one of the very few copper core socket 478 coolers that I know of. It's not the best design. Zalman went through their circular cooling phase, and then everything went toward tower designs, but if you have a well ventilated case, and some decent thermal grease, this should get you where you want to go.
The Celeron Northwood came is several flavors, the fastest being 2.8Ghz if I recall correctly, so pushing past 3Ghz shouldn't be too far of a stretch. What are your temps above 3Ghz?
http://www.coinfo.cefetpb.edu.br/profes ... ations.htmHad to dig for that. Your TJmax should be around 72-74C, so if you can keep it in the low 60's without adding voltage you should be good to go. If you run into a wall check your memory divisor before adding voltage. The first sign of instability with a FSB overclock is usually due to pushing the RAM too far out of spec. Try not to add any voltage if possible because the old Netburst architecture can get hot quick.
Have you bothered to try overclocking the video card yet?