bougth this imac 2011 27" really cheap, too cheap perhaps... it was 300 euro cheaper then what other people were selling it for secondhand. this is my first mac computer, i see people buying secondhand macs and after a while it gets locked! iCloud lock or efi lock. so im really scared to set it up for icloud or upgrade to mountain lion it has been working fine now for 1 week. please help me, what can i do i think factory reset isnt enough right?