Hello, I am new to this site and to being a mac user. I recently purchased a 2011 macbook pro from a friend of mine, and need some assistants in resetting or formatting the computer to make it as if it was just taken out of the box. I have done a little research already and noticed that I may need the os x install disk, in which I did not recieve from my friend. So my ?s are where do I start and a step by step guide through this process would be so.greatly appreciated. Thank you in advance for any and all info. Reguarding my ?s.