What are trying to remove a heatsink from? If there are no mounting screws it is probably glued on. Some people have had luck removed heatsinks by placing the item in the freezer overnight then applying gentle force to remove the heatsink.
Remember, this method is not without danger. It is possible to damage the chip the heatsink is on. Removing the heatsink may also void the warranty.
Remember, this method is not without danger. It is possible to damage the chip the heatsink is on. Removing the heatsink may also void the warranty.