I have a GF2 Ultra OEM made by Visiontek (been a stellar card, still is) and that sucker is epoxied on there I'm assuming. I heated it with a hairdryer but still it required more force than I was willing to provide. My solution was to mount an 80mm Panaflo L1A with plastic ties that run through holes found at the edge of the card. It hangs at an angle and sweeps across the heatsink (the tiny fan on the card is unplugged), then exits out the case bottom because I have removed the slot guards. Better cooling and quieter even.
Good luck with whatever you try.