I'm selling my MacBook tomorrow and was just erasing my hard drive. It currently has 10.7.4 on it. I did the disk utility erase the hard drive and wrote over my only partition which is called Macintosh hd. I was thinking though that I'm supposed to do the actual hard drive instead but it says it can't unmoumt the drive. Currently it is booted up in the command R mode. Does it make sense that it can't be unmounted? Does that part need to be erased? Also, is choosing the rewrite three times option good enough or do I need to go up another level?