John, there's a reason that about 50 people looked at your post and only three answered.
I will, however, expand on RJR's post. You need to look at three guides: a general on on overclocking C2D's, a general one on CPU temperatures and voltages, and a specific one about your model of motherboard.
And for coolers:http://www.frostytech.com/top5heatsinks.cfm
And we want you to do some of your own research for two reasons. First, you need to know enough of what we are talking about to understand our answers. And second, because every motherboard, CPU (even two adjacent ones from the same die), and memory stick is a little different, a cookbook approach will not work.
----------Overclocking since 1978 - Z80 (TRS-80) from 1.77 MHz to 2.01 MHz