I would recommend keeping the hard drives if they have a good amount of storage space on them. Never know when you will need a storage upgrade! But if you definitley need the hard drives gone, This is probally a [https://www.google.com/search?q=how+to+destroy+a+hard+drive&safe=active&rlz=1C1CHBF_enUS767US767&tbm=isch&source=lnt&tbs=itp:animated&sa=X&ved=0ahUKEwiKsKXl1I_YAhVFRiYKHVXSAcEQpwUIIA&biw=1440&bih=769&dpr=1#imgrc=vJfRRy1U7nWv8M:|fun way] But if this at work, ask your boss.