I have an Intel E29477 heatsink with those push-pin quarter turn fasteners in the corners. I just replaced my motherboard and apparently didn't get the thermal compound on right when installing the heatsink on the new motherboard.
I've been trying to remove the heatsink to reapply the thermal compound, but it won't budge. The little black tab just won't come up on two of the four fasteners. I've yanked on it pretty hard with pliers and it stays put.
I've already done this once when removing from the old motherboard, so it's not that I forgot to turn the tabs. This is one of the tabs in question: I'm pretty sure I've got it turned the right way.
Is there anything I can do short of breaking the white tabs off and buying a new heat sink?