P4 Fan to Arctic Cooling Fan
 

I would like to switch from the stock P4 heatsink to the Arctic Cooling heatsink (Super Silent 4Pro L) due to noise reasons (3.2 GHz Prescott).

Is the thermal compound really necessary and where exactly does it go and how much and all that sorts.

yes yes yes yes... ya gotta use thermal compound...

some heatsinks come with a pad on it already...

you put a very thin layer of the compound on the top of the processor.... like paper thin layer.. you do not want it to squish out when you strap the heatsink on...

Thermal compound is absolutely necessary. It's the medium for heat transfer between the processor and the heatsink.

Here are instructions on how to apply thermal compound:

http://www.arcticsilver.com/instructions.htm

Yeah, get you some good Arctic Silver (not the compound that more than likely came with your heatsink) and fire away.

Also, you may want to take a look at lapping your new heatsink. My heatsinks were pretty far out of whack when I got them, but a good lapping made them perfect. If you need info on how to lap let me know, I have 2 or 3 good links. It isn't hard at all, just time consuming. :)

The trick is to go *very* light on the thermal compound. Its only there to fill in the microscopic air holes on the surface of the heatsink and processor. Anything more and it will impede heat transfer rather than help it.