There is a collection of comments and answers on this subject [http://www.ifixit.com/Answers/View/44267/How+do+I+replace+heat+sink+with+both+thermal+paste+and+pads|here] if you want to read more, but my preference is to remove and discard the blue pads. The new Arctic Silver will replace it and do the job of transferring heat into the heat sink. As noted in the [guide|744|thermal paste guide], the underside of the heat sink and the tops of the processors should be carefully cleaned before applying the Arctic Silver.