I'm going to return a rMB I just got yesterday and the last time I did this with a mac I wiped the hard drive and took it to the store. When they turned it on it was a black screen with an indicator in the middle or something. They were trying to figure out what I did, I know I wiped the hard drive, but I guess I also wiped out the OS X? I was really confused, and they didn't know what I did and it was a headache. I just want to make the OS like day one with no trace of any of my data.