I've never tried it, but I found this here click here
1. Remove the OEM heatsink on the processor. You may have to cut off the plastic pins which are holding the OEM heatsink.
2. Use a hairdryer to blow warm air to the heatsink so to soften the compound under the heatsink. You then can easily twist to separate the sink off the processor.
3. Clean up the compound left on the processor, using any common solvent. (Rubbing alcohol, isopropyl alcohol, should be just fine).