Reseat Radeon 9600 64 MB Heat Spreader?

[Tim M]

When upgrading my CPU, the only way I could remove the fan and heat sink was to separate the GPU's heat spreader from the core and memory modules (the black thermal pad would not budge). There was a simple white thermal adhesive holding the heat spreader onto the GPU proper, which I replaced with AS 5. However, under heavy graphics load, the GPU rapidly heats to an unacceptably high temperature that results in warning beeps from the machine. I am using NHC to undervolt the CPU and manage fan speeds.

Is there a method for reattaching the heat spreader in a way that will restore most of the original heat transfer capability (perhaps using AS thermal adhesive)? I'm also wondering if the black thermal pad could be replaced with something else (such as a suitably thick 1" by 1" block of polished copper) to further improve heat transfer.

I would also entertain undervolting the GPU, but there seems to be no simple way of doing this with available software tools despite extensive searching.

Thanks in advance!