I backed up my mountain lion equipped mac then restarted by holding down option and R so I can wipe my disk clean again to do a fresh install of ML again. However, it only gives me the option to reinstall. I have my thumb drive with the lion installer so why is it not booting up from that? Also, when i try to reinstall ML, it continuously ask me for my Apple I.D. even after putting it in correctly. What am I doing wrong?