Hello, you have to restart by pressing cmd + and then when the disks appear, choose the one that is not blocked. because in the recovery hd are the installation data was unlocked and if you could write on it and would lose the mac os x lion. normal hard disk should be called macintoch hd or something. hd recovery partition is the way you have to reinstall every time you want but is read-only. if you need to delete the previous user, and data, you have to be formatted before. for that right from the installation menu, you'll disk utility, you want the hard drive and give it to delete (mac os journaled) then you put out. and there if you give reinstall. Greetings, I hope everything goes well.