(You didn't clarify whether the heatsink/fan unit is still in place,
so what follows assumes that it's still in place; if not, see above.)
Here are 2 quick photos of a stock Intel HSF for the PGA-478 socket:
Once the locking levers are released, you may need to pry the 4 plastic ends
of the fan housing away from the heatsink; then, you can disassemble the
Often, the thermal paste has hardened, and you'll need to rotate the
metal heatsink clockwise then counter-clockwise, to break that bond.
Hope this helps.