So I bought a 13" MBP about 9 days ago. I've decided I want the Retina after all so I want to return the one I currently have. I didn't put much on the computer in these last few days but I have logged into my email accounts, iCloud etc, so just to make sure, I want a clean install. I tried following the instructions on the Apple website but I got stuck where it asks to select the start up disk and erase it. There's 4 different options I believe. 1. 500.11 GB Apple HDD ############ Media 2. Macintosh HD 3. disk1 4. Mac OS X Base System. Which one do I have to choose and after it is erased, will I be given an option to reinstall OS X? I read that there's a recovery partition built into Mountain Lion, but I don't see it (should I see it?) and I'm afraid once I erase the disk I'll be stuck with no OS. I also don't have a USB flash drive atm.