Heres some tips for taking off video card HS`s.
If there are some clips on the rear of the card, press the clips in, and the HS will come loose
If it does`nt come loose, then its using some sort of epoxy and/or clips.
To remove the HS if it has epoxy, either
1) Place card in anti static bag, seal up well, and place in a freezer. Leave for an hour, remove card from freezer/anti static bag, and pull the HS. It should then come off.
2) Place a strong, flat piece of material, near the edge of the HS(like a credit card), then, using the material as protection for the card, lever the HS off using a strong object(such as a blunt knike). Level two corners till its visiably lifted off the core. Then pull the HS off.
Hope this helps.