That cooling blook is secured in the same way as a fan. there are two plastic pins that go though the video card circuit board that have pop out tabs on them. you squeeze those tabs together with a pair of needle nose plyers and then gently push them back through the holes. Once out, clean the gpu thermal paste off in preparation for the fan installation. New thermal paste on the GPU and install the new fan. That simple!!!
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EVGA 680i, Dual EVGA 8800GT'S (650/950), 4 gigs OCZ DDR2 1066, Intel Q9450 at 3.8 Ghz, Koolance Water Cooled, Dual Plextor16x DL DVD+/-RW. Dual WD 250gb 16mb Cache Sata 3.0. 3DMark06 score = 19,168.