I just bought a mac book pro from a friend and after reading that changing the short name was very difficult, I created a new acct used root to copy and paste all folders from the old acct replacing the new ones'. This is my first mac and I must've done something wrong because now I'm told "you do not have sufficient privileges" when I try to do things. I can't install firefox(which I thought would've just been copied over, I can't even set a new desktop. I hope it's just something simple. Please help and thank you in advance.