How can I remove a heatsink that is stuck to a component soldered onto the PCB?
To assist in removing heatsinks that are held in place with thermal glue, turn unit on, until the heatsink gets to its (typically) very high operating temperature. After unplugging all power to the unit, gently try twisting the heatsink, and rock it away from the i.c.; the additional heat will help soften the thermal (glue) paste. This info came directly from one of the manufacturers of thermal glue - used to hold heatsinks in place on high end video cards.