There may be one thing that everyone is overlooking, especially the ones that are running 59-65C at BIOS.
I thought I mounted the stock HSF on my Celeron D running at 2.53GHz properly. I had BIOS temperatures of 65C and even 80C when on load using Intel's Thermal Monitor(I have Intel Desktop Boards). I thought it was because being based on Prescott, it just ran hot. I was getting freezeups in Diablo 2 and knew it was overheating problem because I had that same problem when thermal paste got messed up after playing around taking out the chip which was a Pentium III so many times. I even bought AS5, which seemed to work a bit, since it brought temps down by 5-7C in BIOS, but I screwed HSF mount even more and broke one of the mounting plastic(which then I definitely knew I need a new HSF).
So I bought Intel's stock HSF again. What I find is that they are extremely difficult to mount PROPERLY. I found a certain way to mount them properly. Look at the mounting plastic at the side when mounting.
The rules:
1. Push down the mounting plastic in criss-cross fashion to have stability.
2. Look at the side where the mounting plastic is(the one where you push down), and make sure the black part of the mounting plastic goes below the notch on the white part of the plastic.
After I have done that, the temperatures at BIOS went down from 63C average to 48C average(I currently have the mobo out the case and connected just the cables because I don't want to mount the mobo back in the case since I want a new case, so now its at 44C).
There are no more freezeups either. The highest temps I have ever seen doesn't exceed 65C.