I love my Mac Mini, however the lack of portability is really taking a toll here at university. I need to sell this Mac Mini with 500gb HDD, and get rMBP most likely. Anyways, how can I go about a complete successful HDD erase so as not to worry about a future owner accessing any of my stuff? Would I need to take the HDD out and erase it as an external? If so, wouldn't it render the HDD somewhat useless (for the new owner) when first reinstalled into the Mini? Ideally, I would like it where none of my info is on this Mac. Including my personal login account and iCloud features within. Ya' never know, ya know?